"Many have heard about the Great Work: some wants to dedicate themselves to it, but very few people approach the matter seriously." The author of these words thinks that "there is a transcendental alchemy, the alchemy of oneself, necessary prelude for the improvement of the alchemy of elements". The Great Work talks from the interior of this personal alchemy and proposes twelve meditations to work in the heart laboratory. Acclaimed by Fulcanelli and by most of alchemists of XX century, this small book is, without a doubt, the most well-known and spread work of spiritual alchemy of the West.