"The Medieval alchemists hid the Great Arcanum among innumerable symbols and esoteric allegories. This was in order to save it from profanity, and in order for them to avoid being burned alive in the blazes of the Inquisition." - Samael Aun Weor
Alchemy is an ancient science that preserved the method of transforming the base "metal" (a common person) into "gold" (a fully developed human being).
We have many resources about the precious knowledge. Here are some books, articles, and courses to get you started: