They are the “most famous of the secret religious rites of ancient Greece.”
The Eleusinian Mysteries (Greek: Ἐλευσίνια Μυστήρια) were initiations held every year for the cult of Demeter and Persephone based at Eleusis in ancient Greece. Demeter (/dᵻˈmiːtər/; Attic: Δημήτηρ Dēmḗtēr) is the goddess of the harvest and agriculture.
Though Demeter is often described simply as the goddess of the harvest, she presided also over the sacred law, and the cycle of life and death. In Homer’s Odyssey she is the blond-haired goddess who separates the chaff from the grain. Demeter’s emblem is the poppy, a bright red flower that grows among the barley.
Their basis was an old agrarian cult, and there is some evidence that they were derived from the religious practices of the Mycenean period. Mycenaean Greece was the last phase of the Bronze Age in Ancient Greece (c. 1600–1100 BC). It represents the first advanced civilization in mainland Greece, with its palatial states, urban organization, works of art and writing system.
Since the Mysteries involved visions and conjuring of an afterlife, some scholars believe that the power and longevity of the Eleusinian Mysteries came from psychedelic drugs. The rites, ceremonies, and beliefs however, were kept secret and consistently preserved from antiquity.
At some point, initiates had a special drink of barley and pennyroyal, called kykeon, which has led to speculation about its chemicals perhaps having psychotropic effects. The initiates entered a great hall called Telesterion; in the center stood the Anaktoron (“palace”), which only the hierophants could enter, where sacred objects were stored.
Kykeon is mentioned in Homeric texts: the Iliad describes it as consisting of Pramnian wine, barley, and grated goat’s cheese. In the Odyssey, Circe adds some honey and pours her magic potion into it. In The Homeric Hymn to Demeter, the goddess refuses red wine but accepts kykeon made from water, barley and pennyroyal.
The last night of the 9 day ceremony was the Pannychis, an all-night feast accompanied by dancing and merriment. The dances took place in the Rharian Field, rumored to be the first spot where grain grew. That day (22nd Boedromion), the initiates honored the dead by pouring libations from special vessels.
On the 23rd of Boedromion, the Mysteries ended and everyone returned home.
Numerous scholars have proposed that the power of the Eleusinian Mysteries came from the kykeon’s functioning as an entheogen, or psychedelic agent. The use of potions or philtres for magical or religious purposes was relatively common in Greece and the ancient world.
The initiates, sensitized by their fast and prepared by preceding ceremonies, may have been propelled by the effects of a powerful psychoactive potion into revelatory mind states with profound spiritual and intellectual ramifications.
Many psychoactive agents have been proposed as the significant element of kykeon, though without consensus or conclusive evidence. These include the ergot, a fungal parasite of the barley or rye grain, which contains the alkaloids ergotamine, a precursor to LSD.
Psychoactive mushrooms are another candidate. Terence McKenna speculated that the mysteries were focused around a variety of Psilocybe. Other entheogenic fungi, such as Amanita muscaria, have also been suggested. A recent hypothesis suggests that the ancient Egyptians cultivated Psilocybe cubensis on barley and associated it with the deity Osiris.
Another theory is that the psychoactive agent in kykeon is DMT, which occurs in many wild plants of the Mediterranean, including Phalaris and/or Acacia. To be active orally it must be combined with a monoamine oxidase inhibitor such as Syrian Rue (Peganum harmala), which grows throughout the Mediterranean.