Builders of the Adytum teaches through the tarot, and its most distinctive practice is that students are sent the twenty-two major keys in black and white and colour them by hand to instruction. The point is not decoration. The colour scales come from the Golden Dawn correspondences, and painting a card slowly, in the assigned colours, is designed to fix the associations in a way that reading about them does not. It is a memory technique disguised as an art project.
Paul Foster Case had been a member of a Golden Dawn successor body before founding his own school in the 1920s, and the syllabus shows it: Hebrew letters, the Tree of Life, the tarot as an ordered system, and sound and colour correspondences. What he changed was the delivery. The lessons go out by post, in a set order, at a low cost, and the order has run that way continuously for a century.
Case died in 1954 and Ann Davies led the organisation for the next two decades, which is worth noting in a field where succession usually produces a schism. It did not here. The order continues, headquartered in Los Angeles, with the same correspondence structure and much of the same material, and it remains one of the few Western esoteric bodies whose curriculum has stayed recognisably intact for a hundred years.