Philosophers' stone, conceptual illustration. The three-headed monster held in the alchemical flask represents salt, sulphur, and mercury, the central elements in western alchemy. The colour changes are those the philosophers' stone goes through during transmutation. The philosophers' stone was a mythical substance that was able to turn base metals such as lead into gold and was thought to be a rejuvenating elixir of life. Reproduction after Salomon Trismosin, Splendor solis (1582).