Arthur Edward Waite
Arthur Edward Waite (1857-1942) was a prominent occultist, freemason, and scholar, and an archrival of Aleister Crowley.
Today he is probably best known as the designer of the Tarot card deck illustrated by Pamela Colman Smith, an early colleague of his in the Hermetic Order of the Golden Dawn, which is best known as the Rider-Waite deck after its official publisher. Waite also wrote the accompanying Pictorial Key to the Tarot. However, among his many other books some regard The Holy Kabbalah as the greatest, concerning the same tradition of Jewish mysticism. His other works include The Book of Ceremonial Magic (a revision of The Book of Black Magic and of Pacts) and A New Encyclopedia of Freemasonry.
After they had left the Golden Dawn to found separate breakaways, Crowley wrote a novel with a villain "Arthwait" based on Waite.
Because of his association with Aleister Crowley he has been the source of occasional speculation, although nothing in the series particularly points to Waite as any sort of influence.