Sensory deprivation as a trigger for esoteric experience is exactly what John C. Lilly studied until his death of drowning after a ketamine overdose. He reported experiences including telepathic conversations with dolphins, artificial intelligence as a foe of humanity, and a spiritual hierarchy overseeing human life. I think the whole concept of the isolation tank was invented by him. He was the original inspiration for the 1980 metaphysical sci-fi film Altered States. He had inspired lesser known science fiction stories before then.

20th century mystic Neville Goddard advised seeking "a state akin to sleep" when one is drowsy, the body is inactive, and the mind is just active enough for the will to hold to a visualization of one's deepest desire as already fulfilled. Discussions of his work now are full of references to SATS.

Mocha Amphibious Moose