Ouroboros
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The ouroboros or uroboros is an ancient symbol depicting a serpent or dragon eating its own tail. The ouroboros entered Western tradition via ancient Egyptian iconography and the Greek magical tradition. It was adopted as a symbol in Gnosticism and Hermeticism and most notably in alchemy. Some snakes, such as rat snakes, have been known to consume themselves.
An ouroboros in a 1478 drawing in an alchemical tract
First known representation of the ouroboros, on one of the shrines enclosing the sarcophagus of Tutankhamun
A highly stylised ouroboros from The Book of Kells, an illuminated Gospel Book (c. 800 CE)
Engraving of a wyvern-type ouroboros by Lucas Jennis, in the 1625 alchemical tract De Lapide Philosophico. The figure serves as a symbol for mercury.
August Kekulé
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Friedrich August Kekulé, later Friedrich August Kekule von Stradonitz, was a German organic chemist. From the 1850s until his death, Kekulé was one of the most prominent chemists in Europe, especially in the field of theoretical chemistry. He was the principal founder of the theory of chemical structure and in particular the Kekulé structure of benzene.
1964 West German centenary stamp for the discovery of the molecular formula of benzene