The first floatation tank (or isolation tank) dates back to the late 1950s, when Dr. John Lilly invented it for the study of sensory deprivation.
While working in the laboratories of the National Institute of Mental Health, Dr. Lilly found a large tank used during World War II to study the behaviour of military divers. He decided to adapt it to his purposes in order to investigate the effects of sensory deprivation on the human brain and on altered states of consciousness. At the time, the scientific debate was about the possibility for the brain to stop working in the absence of sensory stimulation. To investigate this possibility, John Lilly adapted the tank in order to allow minimizing external stimuli while floatation.
Originally the tank allowed the experimenter to stay in a vertical position, but later the studies continued on a horizontal position. It was filled with water saturated with Magnesium Sulphate and kept constantly at body temperature in order to eliminate the tactile feel. The experimenter’s body could float in weightlessness in an isothermal liquid. The absence of other stimuli was guaranteed by isolating the tank and the environment from lights and noise.
John Lilly secretly experimented the tank on himself, keeping his organism in the absence of stimuli for many hours: from these experiences, he understood that not only the brain did not stop working, actually floatation had given him the feeling of the deepest rest he had ever felt. After his studies the sensory deprivation tank became a widespread tool to achieve relaxation, well-being and inner introspection.