The ancient Greek Eleusinian mysteries still remain a mystery.
Revealing what occurred at the rites was punishable by death. Many writers mention the mysteries, but no one describes what took place.
What we do know is that every year, in September in October at harvest time, any wars in progress were suspended for two months, for the celebration of the Greater Mysteries. A festive procession of thousands of people went from Athens to the grove at Eleusis, dancing and singing. The Lesser Mysteries took place in February.
Initiates had to apply and be accepted by the priestesses. Fasting, they participated in a two-day ritual of prayer, sacrifice, and re-enactment of the myth of Demeter and Persephone. Over many years, initiates could advance in the religious hierarchy, learning new mysteries and rituals.
Participants in the Mysteries probably drank a psychedelic drug based on ergot, dissolved in wine.
The Homeric Hymn to Demeter gives an account of the rituals and processions leading up to the Mysteries in the Eleusinian Grove, as does Apuelius's book The Golden Ass.
Details of the Mysteries
The Greater Mysteries actually lasted for nine days. On the day before the Greater Mysteries, after rituals and sacrifices, the holy objects were carried in a procession from Eleusis, stopping at the sacred fig tree, and ending at the Temple of Demeter in Athens, near the Acropolis.
On the first day of the Mysteries, the Archon read a proclamation in the agora, summoning the new candiates for initiation. To be a candidate, you could not be a murderer and had to understand Greek. Initiates washed their hands in a sacred basin at the Temple of Demeter.
On the second day, initiates bathed themselves and a young pig in the ocean at Piraeus, the port of Athens; then sacrificed the pig. The third day was a day of sacrifice as well, when representatives of major Greek cities sacrificed many animals. If you have read the Odyssey or Iliad you may realize that a sacrifice was actually a huge barbecue -- the bones and fat were burned to the gods, but the people got to eat the roast meat.
The fourth day was a day of purification and healing, called the Asklepia. The fifth day was the Pompe, or procession, day. The initiates, officials, and new candidates walked 14 miles to Eleusis, a small town to the northwest of Athens. The "party" god Iacchos - god of noise, confusion and excitement - was honored. At various river crossings, there were ribbon dances, the yelling of rude and vulgar insults at the new initiates, music and singing.
The sixth day, at Eleusis, was a day of fasting and further purification. The sacred objects, or heira were shown to the people by the Hierophant, and things were said and done that still remain a mystery. Details of the seventh and eighth day rituals are unclear, though many historians have speculated about psychedelic drugs and ceremonies of death, sex and rebirth.
On the ninth day, people returned to Athens and the religious official, the Archon Basileus, reported details of the ceremonies to the Athenian assembly at the Temple of Demeter.
The Homeric Hymn to Demeter, written about 600 B.C.
Mylonas, George E. Eleusis and the Eleusinian Mysteries. Princeton University Press, 1961.