On the day of the 20th and on through the 21st, the mustai are taken blindfolded through a series of purifications and consecrations, one at a time. Each has a guide who had been initiated in a preceding year (referred to by Plutarch, Moralia, 765A), who could now see the procedures and so becomes an Epopt, “witness.” Candidates are seated on a low throne, with left foot on a fleece, veiled and holding a torch, with a priestess holding a winnowing basket overhead, as priests and/or priestesses dance in a circle, singing around them. (See Dio Chrysostom, Discourse 12, 33; Plato, Euthydemus 277d; Eph. Arch. 1885, p. 150. Gilbert Murray, Five Stages of Greek Religion, p. 23, says the Dadouchos is the initiator during this stage. If Aristophanes, Clouds, 259ff, is not just foolery, the mustai are also sprinkled with flour or chalk at some point.)
Judging from the “password” quoted by Clement of Alexandria — “I have fasted; I have drunk the kykeon; having worked with what I took from the basket, I placed it in the chest, then back in the basket” — each initiate works a ritual with some of the sacral objects in the baskets that the priestesses carried on their heads in the procession. Clement (Protreptikos, 2.18-9) lists what these objects were: sesame cakes, pyramidal and spherical cakes, cakes with many navels, balls of salt, a Dionysian snake (which is obviously a phallic symbol), pomegranates, fig branches, fennel stalks, ivy leaves, round cakes, poppies, marjoram, a lamp, a sword, and a “comb,” which Clement explains is a euphemism for something that represents the female genitals. Perhaps the ritual worked involved placing the phallic symbol in the vaginal symbol, as some have guessed, but obviously innumerable different kinds of rituals were possible with such objects. Clearly Psellus’ third icon fits here, but with a different interpretation.
BTW, just so you know all this is reasonably reliable, I had to write a closed-book, timed examination onit as one of my doctoral comprehensives. That was under the supervision of the late Joseph Fontenrose (actually, he passed over about 1985), Professor Emeritus and former Chair of the Department of Cllassics at UC Berekey, who gave me a High Pass on it. As preparation for it, I read through the 50 pages on the Mysteries in Walter Burkert’s Homo Necans–in German, because there was no English translation yet. That’s the most use I’ve gotten out of that language in my adult life, aside from translating some poetry.
Actually, I had asked several other Classics professors at UCB to be on my doctoral committee, but when I explained that I wanted to study the Mysteries, I was told, “Oh, that’s not fashionable to study there days. You ought to study thus-and-such,” which was always a topic of very little significance, whereas I knew that the Mysteries were far more important for understanding the actual nature of Greek religion, which was the other major foundation for all of Western religious history. Further, the idea that scholarship should be based on whatever is currently fashionable among academics seemed utterly bizarre to me. And sometimes I was told, “Oh, you can’t study that. Too much of it falls in that other department’s turf. You need to restrict yourself to this area here.” Goddess forbid one should set off an academic border skirmish. But I have observed that the truly important questions have ramications for which academic specializations are irrelevant. (As Robert Heinlein said, “Specialization is for dinosaurs.”) I have certainly found few other people who can see why mathematical modeling is usefol for studying theology, although there is some comprehension of why quantum mechanics needs tobe foundational for a future religion adequate for a rapidly evolving modern world. I do plan to blog about all that, as soon as I can get around to it. At the moment, struggling with lesson prep for three brand-new courses, for which I have to teach out of other people’s syllabuses (syllabi?), is a great deal like working for a living. To paraphrase Marx, “Work is the curse of the thinking class.”