In his book, the Immortality Key, Brian Muraresku. Explores the hidden possibility of the presence of psychedelics in the mystery religions of ancient Greece, along with its potential underground continuity within Christianity in the first several centuries after Christ. Brian most notably dives into the Eleusinian mysteries, which were secretive mystery-cult initiations held in the ancient town of Eleusis from around 1500 BC to 391 AD. The upper echelon of Classical society, ranging from Plato, Aristotle, Socrates, Cicero, to Marcus Aurelius all made the trek to participate in the rituals. A ritual so important to these greats that they believed life, “in the absence of Eleusis, would be unliveable”.
Brian goes over a wealth of well documented academic research to support his hypothesis that they within the potion so integral to the ceremonies there contained psychedelic compound(s). The prime suspect being ergot, a fungus that grows on wheat and barley and which contains the chemical first synthesized by Albert Hofman known as LSD. The investigation runs into dead end after dead end due to the lack of remaining archeo-chemical evidence left over from ancient times. However, found in an Eleusis-esque shrine in the Hellenic community of Emporion (located in modern Catalonia) were residues of ergot in a ritualistic drinking vessel uncovered in a study of chemical analysis.
For anyone interested in this subject, I highly recommend Brian's book which combines well-documented academic research with an adventure story taking place in his 10-year long inquiry into the subject during his spare time working as a lawyer.
It is quite possible that those who have used psychedelics tend to look at the world through a psychedelic-centric lens due to the overpowering nature that meets everyone who partakes in the experience, assuming that all history and all that is "good" and "cultured" in the world simply must have originated from this overpowering experience that would have certainly thrown any curious ape for a loop back in our prehistory. However, Brian himself has never tried psychedelics out of respect for the inquiry and desire to maintain integrity in his research, which makes the book a quite objective read on the subject.
In the end, Brian's book raises more questions than answers, but they are important questions to ask nonetheless. What does it mean that the society which all of Western civilization has sprang from, had perhaps been inundated with ceremonies of such entheogenic magnitude? What conclusions can we come to in regards to the role of psychedelics in modern society if our tradition of democracy, egalitarianism, law, and philosophy perhaps possesses a psychedelic heritage? Only time will tell.