the base material of alchemy, in which lay the possibility of gold, was called Saturn, and this base material, as well as having a concrete existence, was also considered to be the alchemist himself.
Greene establishes Saturn as the alchemical prima materia, identifying the planet with the raw, transformable substance of the psyche itself—the ground from which individuation’s gold must be extracted.
, Saturn: A New Look at an Old Devil, 1976thesis