An article from the 60’s on LSD and the ‘third eye’, or more accurately, the role of serotonin in psychedelic states.

the mystery of the LSD-serotonin antagonism persisted. Serotonin is not an unusual chemical in nature; it is found in many places–some of them odd, like the salivary glands of octopuses; others ordinary: it abounds in plants; bananas, figs, plums are especially rich in it. What was it doing in the brains of humans? What was its evolutionary history? In 1958 a Yale Medical School professor of dermatology named Aaron B. Lerner published a paper on the pineal gland which placed this elusive substance in some vague kind of historical perspective and provided for it a real functional role in the brains of mammals.