There were many types of alchemy. The most entertaining are the wildly-descriptive allegories, and one of the best and earliest is the vision of Zosimos of Panopolis. Writing to his sister or student  Theosebia around 300 A.D. he describes the alchemical experience from a very personal point of view, as though he is more interested in what alchemy is doing to him than what he is doing with alchemy.

Of all the early alchemists, Zosimos has the best claim to being a real person. We have other accounts of his public speaking and letters to Theosobia from Alexandria.

Zosimos provides the earliest definition of what alchemy is: "the composition of waters, movement, growth, embodying and disembodying, drawing the spirits from bodies and bonding the spirits within bodies." This is a core Platonic belief that all matter is prima materia with the Aristotelian belief that it is the properties which change that modifies matter, and that by pulling out the properties (the spirit of matter) and refining it, then putting it back into the prima materia, transmutation if effected.

He believed that the process of alchemy has a high purpose, to perfect humans. The alchemist is working with the soul of matter as a priest works with the souls of men. In his work Concerning the true Book of Sophe, the Egyptian, and of the Divine Master of the Hebrews and the Sabaoth Powers, Zosimos wrote:

There are two sciences and two wisdoms, that of the Egyptians [ie. Cleopatra] and that of the Hebrews [ie. Mary the Jewess], which latter is confirmed by divine justice. The science and wisdom of the most excellent dominate the one and the other. Both originate in olden times. Their origin is without a king, autonomous and immaterial; it is not concerned with material and corruptible bodies, it operates, without submitting to strange influences, supported by prayer and divine grace.

The symbol of chemistry is drawn from the creation by its adepts, who cleanse and save the divine soul bound in the elements, and who free the divine spirit from its mixture with the flesh.

As the sun is, so to speak, a flower of the fire and (simultaneously) the heavenly sun, the right eye of the world, so copper when it blooms—that is when it takes the color of gold, through purification—becomes a terrestrial sun, which is king of the earth, as the sun is king of heaven.

He was a Gnostic (see Alchemy 14 Interlude) and wrote (using a very modernized vocabulary of 1818): 

The ancient and divine writings say that the angels became enamoured of women; and, descending, taught them all the works of nature. From them, therefore, is the first tradition, chema, concerning these arts; for they called this book chema and hence the science of chemistry takes its name.

 

He believed that alchemy and the related arts were taught to humanity by the dark angels who came to earth and took human wives. This is one of three accounts that put these arts as god-given. The tales of Hermes Trismegistus (Alchemy 15) and of Pandora are the other two. 

We can't even begin to duplicate the process he is describing, but who cares: it's so much fun to read!

The translation from Of Virtue, Lessons 1 - 3 is from F. Sherwood Taylor, “The Visions of Zosimos,” Ambix 1,1 (May 1937): 88–92

Lesson 1.
The composition of waters, the movement, growth, removal, and restitution of corporeal nature, the separation of the spirit from the body, and the fixation of the spirit on the body are not due to foreign natures, but to one single nature reacting on itself, a single species, such as the hard bodies of metals and the moist juices of plants.

And in this system, single and of many colours, is comprised a research, multiple and varied, subordinated to lunar influences and to the measure of time, which rule the end and the increase according to which the nature transforms itself.

Saying these things I went to sleep, and I saw a sacrificing priest standing before me at the top of an altar in the form of a bowl.2 This altar had 15 steps leading up to it. Then the priest stood up and I heard a voice from above saying to me, ‘I have accomplished the descent of the 15 steps of darkness and the ascent of the steps of light and it is he who sacrifices, that renews me, casting away the coarseness of the body; and being consecrated priest by necessity, I become a spirit.’ And having heard the voice of him who stood on the bowl-shaped altar, I questioned him, wishing to find out who he was. He answered me in a weak voice, saying ‘I am Ion, the priest of the sanctuary, and I have survived intolerable violence. For one came headlong in the morning, dismembering me with a sword, and tearing me asunder according to the rigour of harmony. And flaying my head with the sword which he held fast, he mingled my bones with my flesh and burned them in the fire of the treatment, until I learnt by the transformation of the body to become a spirit.’

And while yet he spoke these words to me, and I forced him to speak of it, his eyes became as blood and he vomited up all his flesh. And I saw him as a mutilated little image of a man, tearing himself with his own teeth and falling away.

And being afraid I awoke and thought ‘Is this not the situation of the waters?’ I believed that I had understood it well, and I fell asleep anew. And I saw the same altar in the form of a bowl and at the top the water bubbling, and many people in it endlessly. And there was no one outside the altar whom I could ask. I then went up towards the altar to view the spectacle. And I saw a little man, a barber, whitened by years, who said to me ‘What are you looking at?’ I answered him that I marvelled at the boiling of the water and the men, burnt yet living. And he answered me saying ‘It is the place of the exercise called preserving (embalming). For those men who wish to obtain virtue come hither and become spirits, fleeing from the body.’ Therefore I said to him ‘Are you a spirit?’ And he answered and said ‘A spirit and a guardian of spirits.’ And while he told us these things, and while the boiling increased and the people wailed, I saw a man of copper having in his hand a writing tablet of lead. And he spoke aloud, looking at the tablet, ‘I counsel those under punishment to calm themselves, and each to take in his hand a leaden writing tablet and to write with their own hands. I counsel them to keep their faces upwards and their mouths open until your grapes be grown.’ The act followed the word and the master of the house said to me, ‘You have seen. You have stretched your neck on high and you have seen what is done.’ And I said that I saw, and I said to myself, ‘This man of copper you have seen is the sacrificing priest and the sacrifice, and he that vomited out his own flesh. And authority over this water and the men under punishment was given to him.’

And having had this vision I awoke again and I said to myself ‘What is the occasion of this vision? Is not this the white and yellow water, boiling, divine (sulphurous)?’ And I found that I understood it well. And I said that it was fair to speak and fair to listen, and fair to give and fair to receive, and fair to be poor and fair to be rich. For how does the nature learn to give and to receive? The copper man gives and the watery stone receives; the metal gives and the plant receives; the stars give and the flowers receive; the sky gives and the earth receives; the thunderclaps give the fire that darts from them.

For all things are interwoven and separate afresh, and all things are mingled and all things combine, all things are mixed and all unmixed, all things are moistened and all things dried and all things flower and blossom in the altar shaped like a bowl. For each, it is by method, by measure and weight of the 4 elements, that the interlacing and dissociation of all is accomplished. No bond can be made without method. It is a natural method, breathing in and breathing out, keeping the arrangements of the method, increasing or decreasing them. When all things, in a word, come to harmony by division and union, without the methods being neglected in any way, the nature is transformed. For the nature being turned upon itself is transformed; and it is the nature and the bond of the virtue of the whole world.

And that I may not write many things to you, my friend, build a temple of one stone, like ceruse in appearance, like alabaster, like marble of Proconnesus, having neither beginning nor end in its construction. Let it have within it a spring of pure water glittering like the sun. Notice on which side is the entry of the temple and, taking your sword in hand, so seek for the entry. For narrow is the place at which the temple opens. A serpent lies before the entry guarding the temple; seize him and sacrifice him. Skin him and, taking his flesh and bones, separate his parts; then reuniting the members with the bones at the entry of the temple, make of them a stepping stone, mount thereon, and enter. You will find there what you seek. For the priest, the man of copper, whom you see seated in the spring and gathering his colour, do not regard him as a man of copper; for he has changed the colour of his nature and become a man of silver. If you wish, after a little time you will have him as a man of gold.

Lesson 2.
Again I wished to ascend the seven steps and to look upon the seven punishments, and, as it happened, on only one of the days did I effect an ascent. Retracing my steps I then went up many times. And then on returning I could not find the way and fell into deep discouragement, not seeing how to get out, and fell asleep.

And I saw in my sleep a little man, a barber, clad in a red robe and royal dress, standing outside the place of the punishments, and he said to me ‘Man, what are you doing?’ And I said to him ‘I stand here because, having missed every road, I find myself at a loss.’ And he said to me ‘Follow me.’ And I went out and followed him. And being near to the place of the punishments, I saw the little barber who was leading me cast into the place of punishment, and all his body was consumed by fire.

On seeing this I fled and trembled with fear, and awoke and said to myself ‘What is it that I have seen?’ And again I reasoned, and perceiving that the little barber is the man of copper clothed in red raiment, I said ‘I have understood well; this is the man of copper; one must first cast him into the place of punishment.’ Again my soul desired to ascend the third step also. And again I went along the road, and as I came near to the punishment again I lost my way, losing sight of the path, wandering in despair. And again in the same way I saw a white-haired old man of such whiteness as to dazzle the eyes. His name was Agathodæmon,4 and the white old man turned and looked on me for a full hour. And I asked of him ‘Show me the right way.’ But he did not turn towards me, but hastened to follow the right route. And going and coming thence, he quickly gained the altar. As I went up to the altar, I saw the whitened old man and he was cast into the punishment. O gods of heavenly natures! Immediately he was embraced entirely by the flames. What a terrible story, my brother! For from the great strength of the punishment his eyes became full of blood. And I asked him, saying, ‘Why do you lie there?’ But he opened his mouth and said to me ‘I am the man of lead and I am undergoing intolerable violence.’ And so I awoke in great fear and I sought in me the reason of this fact. I reflected and said ‘I clearly understand that thus one must cast out the lead, and indeed the vision is one of the combination of liquids.’

Lesson 3.
And again I saw the same divine and sacred bowl-shaped altar, and I saw a priest clothed in white celebrating those fearful mysteries, and I said “Who is this?’ And, answering, he said to me ‘This is the priest of the Sanctuary. He wishes to put blood into the bodies, to make clear the eyes, and to raise up the dead.’

And so, falling again, I fell asleep another little while, and while I mounted the fourth step I saw, coming from the East, one who had in his hand a sword. And I saw another behind him, bearing a round white shining object beautiful to behold, of which the name was the meridian of the Sun, and as I drew near to the place of punishments, he that bore the sword told me ‘Cut off his head and sacrifice his meat and his muscles by parts, to the end that his flesh may first be boiled according to method and that he may then undergo the punishment.’ And so, awaking again, I said ‘Well do I understand that these things concern the liquids of the art of the metals.’ And again he that bore the sword said ‘You have fulfilled the seven steps beneath.’ And the other said at the same time as the casting out of the lead by all liquids, ‘The work is completed.’

The Alchemy Reader (pp. 50-53). Cambridge University Press. Kindle Edition.

Carl Jung, mid-20th-century phychologist, studied alchemy as a possible source of a universal symbolism of dreams. He was very interested in the Visions of Zosimos.

One of Zosimos' texts is about a sequence of dreams related to Alchemy, and presents the proto-science as a much more religious experience. In his dream he first comes to an altar and meets Ion, who calls himself "the priest of inner sanctuaries, and I submit myself to an unendurable torment." Ion then fights and impales Zosimos with a sword, dismembering him "in accordance with the rule of harmony" (referring to the division into four bodies, natures, or elements). He takes the pieces of Zosimos to the altar, and "burned (them) upon the fire of the art, till I perceived by the transformation of the body that I had become spirit." From there, Ion cries blood, and horribly melts into "the opposite of himself, into a mutilated anthroparion"—which Carl Jung perceived as the first concept of the homunculus in alchemical literature.

Zosimos wakes up, asks himself, "Is not this the composition of the waters?" and returns to sleep, beginning the visions again—he constantly wakes up, ponders to himself and returns to sleep during these visions. Returning to the same altar, Zosimos finds a man being boiled alive, yet still alive, who says to him, "The sight that you see is the entrance, and the exit, and the transformation ... Those who seek to obtain the art (or moral perfection) enter here, and become spirits by escaping from the body"—which can be regarded as human distillation; just as how distilled water purifies it, distilling the body purifies it as well. He then sees a Brazen Man (another homunculus, as Jung believed any man described as being metal is perceived as being a homunculus), a Leaden Man (an "agathodaemon" and also a homunculus, but see also Agathodaemon the alchemist). Zosimos also dreams of a "place of punishments" where all who enter immediately burst into flames and submit themselves to an "unendurable torment."

Jung believed these visions to be a sort of Alchemical allegory, with the tormented homunculi personifying transmutations—burning or boiling themselves to become something else. The central image of the visions are the Sacrificial Act, which each Homunculus endures. In alchemy the dyophysite nature is constantly emphasized, two principles balancing one another, active and passive, masculine and feminine, which constitute the eternal cycle of birth and death. This is also illustrated in the figure of the uroboros, the dragon that bites its own tail (and which appears earliest in the Chrysopoeia). Self-devouring is the same as self-destruction, but the unison of the dragon's tail and mouth was also thought of as self-fertilization. Hence the text of "Tractatus Avicennae" mentions "the dragon slays itself, weds itself, impregnates itself." In the visions, circular thinking appears in the sacrificial priest's identity with his victim and in the idea that the homunculus into whom Ion is changed devours himself—he spews fourth his own flesh and rends himself with his own teeth. The homunculus therefore stands for the uroboros, which devours itself and gives birth to self. Since the homonculus represents the transformation of Ion, it follows that Ion, the uroboros, and the sacrificer are essentially the same.

Wikipedia - Zosimos of Panololis

The "little man of copper" will become a rather important secret of alchemy, the generation of life in the form of a little human, the homunculus, formed from sperm only. Not until the 1600's will anyone (Paracelsus) attempt to describe the process in writing.

It might be coincidence that the priest is named "Ion," which will later be the name of the things formed in solution when a salt dissolves in water.

Another book of Zosimos, the Book of Pictures, I have never seen nor read. We don't have the original, nor even know if the original book had pictures in it; we only have Arabic versions of the text. Here is what Wikipedia has to say about it:

This book is divided into 13 chapters, each of them being introduced by a separate image. Two chapters contain a whole series of images, which - according to Zosimos’ statements - are meant to be pondered upon in order to better understand his teaching.

The whole text gives a lively dialogue between an alchemical couple: i.e. Zosimos and his female student Theosebeia, revolving about Zosimos' teaching. It reports Theosebeia's complaining about unclear statements of Zosimos as well as Zosimos' anger about her inability to understand his statements. At first sight, the dialogue deals with question upon how to understand statements of alchemical philosophers like Agathodaimon, Democritos, Isis, Moses, Maria [the Jewess], Ostanes, as well as with questions about technical aspects of the alchemical work. But again and again, Zosimos emphasises that he does not talk about the substances and processes as such, as matter, but that they have to be understood symbolically. Zosimos describes the alchemical work by means of a series of images and says to Theosebeia: "What I wrote and told you, and with the picture I made for you with me in it, I gave you what you need to know, and this should be enough for you." He also states, that these images depict his own innerpsychic process of transformation.

Zosimos' teaching is based on the one hand on his own dream visions, reported in the text. Another source for his teaching was his suffering of a passionate love relationship to Theosebeia, being not allowed to be simply lived out physically. This led him to understand the alchemical work as psychic transformation, enabling the adept to hold and contain the fire of attraction. Correspondingly, Zosimos drew symbolic images of his own death and resurrection as explanation for Theosebeia. Following Abt, the book can be regarded as the earliest historical description of an alchemical work based on a psychic transformation.“ And it “is a testimony of the painstaking quest to understand not only the problem but also the meaning of attraction, repulsion and ultimate reconciliation between the outer male and female as well as the inner fire and water” a process that “is described […] with basic substances, mirroring the very elemental, collective character of this process.”

In this book, we find fragments of writings from „The Sulfurs“, which are ascribed to Zosimos and from his “Letters to Theosebeia”. In the course of the dialogue, those fragments seem to be interrupted by Theosebeia's questions and by further explanations. By this, Zosimos’ teaching is presented in an easier and more understandable way, as Abt holds.

With regard to content and style, there are similarities between both books, "the Book of Pictures" and the "Book of Keys".

Up to now, only one single Arabic manuscript of the "Book of Pictures" is extant. In the fourth part of the "Book of the Rank of the Sage (Rutbat al-Ḥakīm) its author Maslama al-Qurțubī (formerly wrongly assigned to Maslama al-Magriti) quotes extensively from the “Book of Pictures”. He is the first author quoting it, but using another Greek original than the one published in 2015 than the version published 2015 (CALA III, by Th. Abt) and has influenced several alchemists like the early Arabic alchemist Ibn Umail, the "Kitab al-Habib" (Book of the Friend/Lover; including a dialogue between a so-called Rusam and Theosebeia) and the alchemist "Hermes of Dendera", author of "Risalat as-Sirr" (Epistle of the Secret; including a similar dialogue between Hermes Budasir und Amnutasiya). Other traits of Latin symbolic alchemy, like the traditional division of the work in 12 parts or the representation of inner and outer relationship between adept and soror mystica (e.g. in "Rosarium Philosophorum" and in "Mutus Liber") can be traced back to this book and seem to be influcend by it. Fragments of the text of the "Book of Pictures" can be found in "Rosarium Philosophorum" and "Artis Auriferae". (e.g. titled "Tractatus Rosini ad Euticiam" (="Treatise of Rosinus to Euticia").

The Book of Pictures itself is influenced by Ancient Egyptian thinking, its iconography showing relations to pharaonic iconography and having motifs paralleling Egyptian books of the underworld like Amduat, which was known until Greek-Roman times. Regarding the inner and outer relationship between man and woman or between psychic male and female aspects, the "Book of Pictures" forms a cultural bridge between pharaonic thoughts and European medieval alchemy.

We know about Mary the Jewess only through the writings of Zosimos. We have none of her original writings.