Spiritual Alchemy

The spiritual alchemy experienced in the Middle Ages its European revival in secret circles.
Books like "Rosarium philosophorum", "Atlanta fugiens", "Philosophia Reformata" and the 22 tarot cards of the Visconti Tarot concealed their secret knowledge into symbols and provoked the attention of the church just as the medieval Rosicrucians.
The alchemy, whose goal of 'making gold' attracted derision, offered a simple way of disguising a mental process, which was hardly practically implemented. Even the esoteric Freemasonry with reference to 'Hiram Abiff' took place in closed circles.
The well known "OM" as Mantram of the indish Raja Yoga was as "O"pus "M"agnum implemented, because the whole process can be achieved - even without detailed secret knowledge and very stolid by bearing in mind a pure way of life and of course with the necessary VAK.
The "Opus Magnum", the
"Great Work of perfection" goes through the steps
1-18 of the Universal Path:

1-8 Preparation
9. Materia Prima
10. Calcination
11. Sublimation
12. Solution
13. Putrefaction
14. Destillation
15. Coagulation
16. Tinctura

17. Multiplikation
18. Projection

Alchemy Levity
Alchemie France
Alchemic Symbols

Michelspacher Cabala: Spiegel der Kunst und Natur, 1615
On the stairs the names of the steps 10-15

Opus Magnum Alchemy Wiki Lapis Philosophorum