The Book of the Sacred Magic of Abramelin the Mage presents itself as Abraham of Worms' account (dated 1458) of learning the operation from the Egyptian mage Abramelin. Surviving manuscripts are 17th-18th century German and French copies. S. L. MacGregor Mathers translated an incomplete French manuscript (1898) with a six-month operation; Georg Dehn and Steven Guth's edition from the German manuscripts (2006) restores an eighteen-month timeline and the full word-squares.
Abramelin is famous for its talismanic word-squares, grids of letters commanding spirits for specific effects, including the SATOR-AREPO family of squares that circulated independently for two millennia. The squares made the book a source text for folk magic far beyond its ritual frame.
The Golden Dawn adopted the Knowledge and Conversation of the Holy Guardian Angel as its central aim, and Crowley made it the core task of his A.'.A.'. system, effectively reinterpreting the operation as union with one's own deepest genius. The demons of the book's second half became, in this reading, the unintegrated psyche's personnel.
If the prerequisite is total retreat, what is the operation actually purchasing?