Ouroboros

I learned about the ouroboros from reading The Wisdom of Insecurity (1951), a book written by Alan W. Watts. You should check him out.

From Wikipedia:

[The Ouroboros, also spelled Ourorboros, Oroborus, Uroboros or Uroborus (IPA: [ˌjʊərəʊˈbɒrəs]), is an ancient symbol depicting a serpent or dragon swallowing its own tail and forming a circle. It has been used to represent many things over the ages, but it most generally symbolizes ideas of cyclicality, unity, or infinity. The ouroboros has been important in religious and mythological symbolism, but has also been frequently used in alchemical illustrations. More recently, it has been interpreted by psychologists, such as Carl Jung, as having an archetypal significance to the human psyche.]