In the 1950s, while working at the National Institute of Mental Health (NIMH), Dr John C. Lilly began experiments to determine what would happen if the brain was isolated from external stimulation. One theory at the time was that the brain would simply shut down and conscious activity would stop. What he found was quite the opposite – the brain remained quite active, while the body achieved an extreme state of relaxation. Originally, floaters sat upright and were completely submerged underwater with a mask to breathe with. Over the years, the tanks have evolved with the addition of Epsom salts, heating, and filtration systems.