"One hour of floating in the tank has the recreational value of three hours of deep sleep." (Dr. John C. Lilly)
Floating in a tank was invented in 1954 by the neurologist and author Dr. John C. Lilly (brain and communication researcher). He was particularly interested in the psychological and physiological effects of meditative states completely shielded from external stimuli.
Lilly found that his subjects in the floatation tank slid into a special state of relaxation just between waking and sleeping - similar to a trance. In the EEG we can recognize that state very clearly at a lowered frequency of brain waves (theta waves), something that is very rarely seen in healthy people, except just during a deep meditation or floating. NASA used floating tanks later to simulate weightlessness and isolation. In the sixties and seventies, the isolation tank was used by adherents of the esoteric era and called Samadhi-Tank (after the Sanskrit term Samadhi for the special state of consciousness in which the viewer and the viewed object melt in one).
Today, more and more people with different expectations consider floating as a ground-breaking technique of relaxation and stress management. It is maybe the most interesting technique of 'medical wellness'.