With my greatest admiration towards Alchemy I have to admit that the more I research, the more complicated it gets till I reach the point I feel totally unable to express my tiny insight of it. Yet I give it a try since lately I had an inspiring discussion about the topic, which triggered me to share that little piece of mine, which I discovered through the last couple of years from Maria Szepes, Jung, Paracelsus, Goethe, Newton, Terence McKenny etc.
Alchemy as per my understanding through how Jung described it, is the Doctrine of Arcana. In that meaning Arcana is the Essence, which holds Health, Wealth and Power in its possession. It means Arcana is the Quinta Essentia - the fifth element - the Spirit of Truth. This is the essence which turns the metal to gold, and also it is the Elixir of Life. It is a living being, it is a the Spirit of the Universe.
However it exists in the Universe in 'Saturnian' (impure) form, which needs to be purified.
While this essence in one hand was searched in the outside World, it also considers a so called "participation Mystique' elements, which makes the researcher involved, which means that the purification process also become an individualization process.
Jung referred it to the Myths of Creation. In the Beginning everything was One, and it was Darkness. And the greatest and highest purpose was hidden inside the Darkest bottom of the Unconsciousness.
In the seed, the life is still One and it has everything, including the fire, which holds life. In that meaning Darkness gives birth to Light.
The aim of Alchemy is to create that 'Lumen Nature' - Natural light by subtract the light-bringer (also called Lucifer) from the Stem Material.
Alchemy in this meaning consists of the separation of the Chaos (Prima Materia) to an active and a passive part and the conjunction, which is the Alchemical Marriage.
That is connected to the Correspondence Law or Opus Alchemicum (As Above so Below) and it states that the Alchemical Marriage can not be done without the completion of the circle. The Earth can not ascend till the Sky does not descend.
This process can not be done without the 'corpus toxicum', the aqua of the philosopher, which makes the transmutation possible.
The Secret is in the Hermetic Vessel, which holds the Wisdom of God.
That Vessel is the rounded pot, jar or stone, which represents not just the Lapis but the Selbst itself. It is also represents a Temple or the awareness, which is able to accept the Selbst. In an other translation it is the Selbst holding the Selbst itself. It is a dual-substance holding the wholeness inside, the harmonized balance of Yin and Yang or the Feminine and Masculine force, which works as a bridge between consciousness and unconsciousness.
As this Sacred Essence is the jar for the consciousness and the unconsciousness as well, it can not be understand by logic and the closest we can get to it is by using the language of symbols.
Jung used an ancient sermon about a fish called cruribus to describe. There is a magnetic stone in its tail-vertebrae. This stone called Opsianus. This is a very rare stone and it is so powerful, that it is able to detain the big, proud ships of the Ocean. This stone is derived from Saturn and black from outside like lead, and white from inside. It is the dual-essence of the Mercury. You need a certain procedure how to catch this fish, and even if you manage to take it out from the water, when you try to remove the stone from the tail, you have to be extremely careful as the dual-substance vaporize when it contacts with Air.
There are lots of symbols in this discription, from the difficulty of the task till the concepts of the 7-steps Alchemical procedure which ends in the Alchemical Marriage, which is the creation of the Philosopher Stone. One caution is important to mention, that the process of the stone requires certain, special, sacred discipline, not only because of the risk that the essence would vaporize but also as it is toxic and if someone tries to reach it without appropriate approach, it can poison him or drive him crazy.
This is one tiny little part of clue about the Philosopher Stone, the Lapis Philosoporum, the Sacred Essence, the Quinta Essentia, the Selbst, the Uroboros, the Essence of the One, the Imago Dei.
"Tis true without lying, certain and most true.
That which is below is like that which is above
and that which is above is like that which is below
to do the miracle of one only thing
And as all things have been and arose from one by the mediation of one:
so all things have their birth from this one thing by adaptation.
The Sun is its father,
the moon its mother,
the wind hath carried it in its belly,
the earth is its nurse.
The father of all perfection in the whole world is here.
Its force or power is entire if it be converted into earth.
Separate thou the earth from the fire,
the subtle from the gross
sweetly with great industry.
It ascends from the earth to the heaven
and again it descends to the earth
and receives the force of things superior and inferior.
By this means you shall have the glory of the whole world
and thereby all obscurity shall fly from you.
Its force is above all force,
for it vanquishes every subtle thing and penetrates every solid thing.
So was the world created.
From this are and do come admirable adaptations
where of the means is here in this.
Hence I am called Hermes Trismegist [sic],
having the three parts of the philosophy of the whole world
That which I have said of the operation of the Sun is accomplished and ended."