Philosopher's Stone
The Alchymist, In Search of the Philosophers' Stone by Joseph Wright of Derby, 1771.
The Philosopher's Stone is a substance that alchemists believed was able to turn base (impure) metals (such as lead) into pure gold. They thought it could also be used for rejuvenation (to become younger again) and to achieve immortality (to live forever).
In popular culture
The first Harry Potter book is called Harry Potter and the Philosopher's Stone (Harry Potter and the Sorcerer's Stone in the United States).
The manga and anime series Fullmetal Alchemist.
Philosopher's Stone Media
The Squared Circle: an alchemical symbol (17th century) illustrating the interplay of the four elements of matter symbolising the philosopher's stone
Philosopher's stone as pictured in Atalanta Fugiens Emblem 21
