Philosopher's Stone

The philosophers' stone is a legendary alchemical substance, supposedly capable of turning base metals, especially lead, into gold, essentially an early attempt at nuclear transmutation. It was also sometimes believed to be an elixir of life, useful for rejuvenation and possibly for achieving immortality. For a long time, it was the most sought-after goal in Western alchemy, meditated upon by alchemists like Sir Isaac Newton, Nicolas Flamel, and Frater Albertus.