alchemy 

«Alchemy (from Arabic: al-kīmiyā) was an ancient branch of natural philosophy, a philosophical and protoscientific tradition practised throughout Europe, Africa, and Asia, (...) In the eyes of a variety of esoteric and Hermetic practitioners, alchemy is fundamentally spiritual. Transmutation of lead into gold is presented as an analogy for personal transmutation, purification, and perfection. (...) Jung discovered a direct correlation or parallels between the symbolic images in the alchemical drawings and the inner, symbolic images coming up in dreams, visions or imaginations during the psychic processes of transformation occurring in his patients

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