Symbols of the synthesis of the Great Work, 1678. 4 sides=4 elements. 3 serpents=tria prima (sulphur, salt, mercury). 2 circles=masculine and feminine properties. Large circle attached to tube=Hermetic Vase. From Tripus Aureus by Michael Maier, a Latin translation of the legendary 15th century German monk Basil Valentine's book on the Philosopher's Stone, and representing the 7th of the 12 keys to the alchemical process. (Frankfurt, 1678).