Pythagoras, then Empedocles, later Aristotle, (and others) were alchemists. They tried to revive the Ancient Alchemy, but also to keep it hidden(to avoid abuse of it), developing systems, spreading hints and hidden knowledge, fully understood only by those who understand its basics.Pythagoras' knowledge of alchemy comes from Hermes(Egyptian Thoth), or more properly said, The Ancient Alchemy Schools of Egypt and The Eye of Thoth, of the same origin as, The Ancient China's Alchemy(origin of Ancient Martial Arts), "Cultivation" of one by comprehending The Laws of The ALL(Dao) to reach Immortality, control over nature, and later, maybe even complete control over the Universe(/create their own before leaving). Also of the same origin as India's Vedic Math/Science/Mysticism.If you are interested to understand alchemy, try to research them* all a little, connect the dots, and find their common origin. Remember to look for the "Earlier", not the "Later" origin of each.* "Egypt's Thoth,China's Tao(/Dao), India's Vedic Math/Science/Mysticism"It is extremely easy to find if you know what youre looking for, as the main base pieces of that origin(/ancient knowledge) are open to the public, and many times even infront of everyones eyes, without you realizing it.The Origin of Ancient Alchemy(symbolized/represent in the form of The Seed/Flower/Fruit/Egg of Life) from all over the world, is of One, same Origin, that goes long before our publicly open, recorded history. Sadly, most of the hidden and restored Ancient Knowledge has burned along with the Ancient Library of Alexandria.Now only few know the truth, and of how Ancient Alchemy really works.So it is literally impossible to find any 'beginner' books for it, etc..And even before that, it has been a tradition to keep the basics of it unwritten, as a test.Those who reach the understanding of those basics, are qualified to advance and study it.