The following are quotations from R Ramsden’s notes of the seminar As above, so below: introduction to alchemy and analytical psychology: main concepts, Cape Town 2012:

Most sources put the origin of alchemy in Alexandrian Egypt, and the religion of the Egyptians and their embalming rituals. The religion of the Egyptians was rooted in a theology of Isis and Osiris, and much of the alchemical language and reference points of medieval alchemy is rooted in this mythology. (p. 1)

Baking of pottery and melting of metals is the beginning of alchemy in the shape it had in Alexandrian Egypt. The art of making pots would lead to the discovery of metals in the earth, and its smelting properties. Metal ore in the earth was seen as embryos in the womb of the mother, ripening in the dark. The alchemist would steal this embryo and hasten it to maturity through capturing it in a vessel and maturing it with fire. Cooking is the earliest form of alchemy, and fire and pot are the basic instruments of alchemy, as water and earth are its basic matter. In this we have the main elements of alchemy: fire, water, earth and air, held together in a creative balance. (p. 2)

Alongside this, the wise of the human race, the shamans, have always been in communication with an inner fire: a spirit of transformation which assisted them in how to live, how to make a way in the world, how to alleviate suffering. The relationship to the inner fire has been the basis of our religions and mythologies, the lens through which we view the world, the guiding principle along life’s path. (p. 2)

Alchemy: the dark art
Dark is not to be understood in our Western view as sinister and evil. Dark is to be understood as the mystery of the invisible realm of Spirit and Soul. Alchemy is therefore a search for understanding of the invisible realities of psyche, soul and spirit, both in us, and in the world. Alchemy was the search to find the secret of spiritual transformation in our material existence. The way this search was expressed and understood was through the search to transform base matter, metal, like lead, into noble matter, a metal, like gold. Psychologically translated, it is the search to understand how to transform an immature and ignorant psyche or human into a mature and wise psyche or human. Alchemists worked in laboratories with the vessel, the matter and the fire. Their aim was to distil out of base matter a refined Spirit which would reside in a Stone, which contained great wisdom and transformative power. They experienced, through intense feeling and visionary participation, that transformation was taking place in them too. As they worked they experienced visions which they developed into ‘Theoria’ through meditation and amplification. These visions were given to them by a mysterious Spirit that dwelled in matter, in them, as well as in the universe. They called this Spirit Mercurius. (p. 5)

The real mystery does not behave mysteriously or secretly; it speaks a secret language, it adumbrates itself by a variety of images which all indicates its true nature. The real nature of matter was unknown to the alchemist: he knew it only in hints. In seeking to explore it he projected the unconscious into the darkness of matter in order to illuminate it. In order to understand the mystery of matter he projected yet another mystery – his own psychic background – into what was to be explained. This procedure was not, of course, intentional; it was an involuntary occurrence. Strictly speaking projection is never made; it happens, it is simply there. In the darkness external to me I find, without recognizing it as such, an interior or psychic life that is my own.  Quoting Jung CW 12, Psychology and alchemy,  par 345–346(p. 6)

One of the most important woman alchemists who lived in Alexandria around 100 AD, was Maria Prophetissa.

Axiom of Maria
One becomes two
Two becomes three
And out of the third comes
The One as the fourth.                                                                                                                                                                   

“I have worked on this Axiom over many years, and have come to understand it as a basic pattern describing the stages of the transformation process from immature ego to the mature viewpoint which embraces the reality of the Other in a functional relationship. The following is my understanding of the Axiom in psychological language:

Stage one is an original, unitary standpoint … no differentiating consciousness yet.
Stage two where separation and differentiation begins, resulting in a consciousness of two.
The third stage begins when the ego enters into a dialectical relationship with the shadow, or anima/animus, or inner figures representing these. This relationship, here represented by the image of the labyrinth, is the Third.
Lastly, from this labyrinthine relationship, which weaves back and forth between the opposites of male and female, above and below, the authentic self is born, a new more balanced viewpoint, which is represented by the image of the Divine child, the Fourth.

These four stages are also represented in alchemical writing by four colours: black, white, yellow and red. In later alchemical writings the yellow was dropped.
Black represents the initial stage of ignorance or unconsciousness, or depression, and is represented as lead.
White represents the second stage, in which the light of consciousness begins to dawn, insight into patterns emerge, literally like the dawning of the day. In the tree image, it is the young plant emerging from the dark earth into the light of day. It is a stage which brings relief from blind depression.
Yellow represents the sunrise as it comes up, and is the highest firing of consciousness. This is a stage of realization of realities of life, of self, of one’s responsibilities and limitation of self and other, and learning to relate to the psyche as a power greater than the ego. The passage to relating is through humility. This is the highest heat of the fire.
Red is the full light of day, the red blood of lived reality in full consciousness and is equated to the birth of the divine child, wisdom, and gold. This is a stage of living the reality of oneself, of acceptance of self and the world as it is, of working creatively within limitation and developing one’s gifts.” (p. 9–11)

Dangers of the art:  
I shall keep silent about this science, which has led most of those who work in it to confusion, because they are few indeed who find what they seek, but an infinite number who have plunged to their ruin.

This stone proceeds from a most glorious place of great terror, which has given over many sages to death. (p. 13 quoting Jung CWV 13 par 429)