"The Eleusinian Mysteries were initiations held every year for the cult of Demeter and Persephone based at the Panhellenic Sanctuary of Eleusis in ancient Greece.0 They were celebrated annually for at least a thousand years until 329 CE. The festival started in early September in Eleusis, a town 14 miles from Athens, and was known as the most mysterious of the ancient Greek world.2 According to the myth told in the Homeric Hymn to Demeter, the earth goddess Demeter went to Eleusis in search of her daughter Kore (Persephone), who had been abducted by Hades (Pluto). The Eleusinian Mysteries are considered the most famous of the secret religious rites of ancient Greece."
And a Link to that Venerable publication, Vice magazine!
https://www.vice.com/en/article/epgebm/ergot-fungus-psychedelic-lsd-witchcraft
"Ergotism was likely discovered when humans began cultivating grain, about 10,000 years ago. Roman scholar Pliny is the first to mention ergot-infested grain much later, in the first century AD, but not until after historians and chemists described the Greeks using the fungus as a chemical weapon and a psychoactive drug during the celebrations of the Eleusinian Mysteries."
An episode of, hmm, Ripley's maybe? attributed the Salem Witch Trials to ergot in the grain supply. It was actually just a sociopathic teen bitch that made the accusations, and then recanted them 20 or so years later, but not before a bunch of superstitious and/or hateful a-holes murdered a bunch of their neighbors.