when Osiris was murdered by the demonic god Seth, the latter shut him into a lead coffin and threw it into the sea… Osiris’ lead coffin was identified with the alchemical retort as early as the third century of this era, and was described as the real ‘secret of alchemy.’
Von Franz establishes the coffin’s central depth-psychological valence by equating Osiris’s lead coffin with the alchemical vessel of transformation, identifying it as the mythological prototype of the retort in which dissolution and rebirth occur.
, C.G. Jung: His Myth in Our Time, 1975thesis