"Les Confidences: Confidential Disclosures" by Alphonse de Lamartine, translated by Eugène Plunkett, New York: D. Appleton & Co., (Book IV, Note VIII, p. 60), 1857.
Carl Gustav Jung, Herbert Read, Michael Fordham, Gerhard Adler (1963). “Mysterium coniunctionis, an inquiry into the separation and synthesis of psychic opposites in alchemy”