Initiation from Problems on the Path of Return by Mark Stavish, M.A. in Vol 3 No 1 of Caduceus.

“Until this century, the most common method of esoteric learning was either through a teacher-student relationship, or affiliation with an esoteric lodge. The principle means of instruction and initiation was often ritualistic, and would involve one or more persons who has experienced ritual or its equivalent previously.” [via]