These source materials appeared between 1900 and 1940 CE.
The Descent of the Dove by Charles Williams (1939)
The Mystical Qabalah by Dion Fortune (1935)
The Karezza Method by J. William Lloyd (1931)
The Sufi Message of Hazrat Inayat Khan: The Art of Personality by Inayat Khan (~1918)
Logos Mantram Magic: Gnostic Secrets of the Rose-Cross by Arnold Krumm-Heller (1914)
Karezza: Ethics of Marriage by Alice Bunker Stockham (1903)
The Majesty of Sex: A Song of Immortal Life by Nancy McKay Gordon (1902)