In his 1927 essay ‘On Being One’s Own Rabbit’, the British-Indian scientist and writer J.B.S. Haldane surveyed the history of an enduring but contentious approach to scientific discovery: self-experimentation. At the age of eight, Haldane tested poison gases on himself in his scientist father’s home laboratory. As an adult, among other self-experiments occasioning losses of consciousness from ‘blows on the head, from fever, anaesthetics, want of oxygen and other causes’, he once induced sufficiently high levels of oxygen saturation to suffer a violent seizure and the crushing of several vertebrae.

Haldane is one of many maverick self-experimenters rescued from varying degrees of obscurity by Mike Jay in Psychonauts, a fascinating account of psychoactive drug exploration in the hundred or so years before the explosion and subsequent suppression of psychedelics in the 1960s and 1970s. As today’s mainstreaming of consciousness-altering drugs like psilocybin and MDMA continues apace, Jay’s book honours these pioneers of the drug experience’s ‘double consciousness’ – the coterminous ‘inner world of dreams and the waking state of reason’ – who imperilled their bodies and, moreover, their minds in the pursuit of knowledge, pleasure, and transcendent experience.

The milieux they inhabited were about as far as you can get from today’s psychedelic clinical trials: literary salons, occult rituals, and smoke-wreathed gatherings from London and Egypt to Morocco, the Far East, and fin de siècle Paris. Their pharmacopeia was equally eclectic: cocaine, nitrous oxide (laughing gas), opium, ether, morphine, chloroform, amphetamines, cannabis (as well as its more concentrated form, hashish), and, later, the psychedelics mescaline (from the peyote cactus), LSD, and psilocybin (from ‘magic’ mushrooms).