Near as anyone can tell, the Celtic Cross comes out of the assorted Golden Dawn materials and was propagated (if not totally invented) by A.E. Waite in the early 20thcentury. Waite was super into the Holy Grail/Celtic religion thing and was, like many of his colleagues, invested in demonstrating how there was a great deal of commonality in the various schools of occult thought, intersecting with ancient religions, etc., etc. Nobody at the time was really above making weak claims as to the antiquity of assorted pieces of occult wisdom, and the Celtic Cross just sort of gently leached into the magical water supply as the tarot’s popularity grew.
If you want to hear people doing cold readings with three-card spreads, listen to the consultation segments of the Lucky Mojo Hoodoo Rootwork Hour podcasts. You might pick up a few tips on divination — and the card readers almost always all three-card spreads.
Unrelated rant. I was watching the miniseries version of Jonathan Strange & Mr. Norrell recently and, once again, the candles! Were there enough beehives in England to make wax for all those candles? Remember, back then the lighting choices were candles handmade from beeswax, high-end oil lamps burning oil rendered from whale blubber, or simple wick-type lamps burning some kind of animal fat or olive oil. That was all! Petroleum-based lighting did not start in a big way until the 1860s.
But if you watch(ed) it, give credit to the costumers and set designers. Those were some of the most authentic-looking c.1800 men’s britches I have ever seen. Note how the men’s styles break on generational lines. You are seeing the 17th-18th century fashion of wigs suddenly ending (except in court) in the space of a few years, and also a total change in women’s styles with the Neoclassical revival.
The interior spaces were done well in terms of furniture, colors, and the general level of crime. But too many candles.
Childermass’s Tarot cards were a treat though. Such a level of greasiness!
The symbols for eta, theta, and epsilon can be clearly seen. Maybe it was used to determine which frat the ancients were going to pledge, but I’d like to think it was used to roll for hit points for warrior and sphinx classes. Now all we need is for someone to 3D-model this so we can print it out and make up our own ancient Egyptian version of D&D.