Question about the insane asylum

Before the days of major tranquilizers there were such "therapies" as hydrotherapy (check it out on Google). I'm not sure of the exact term for this particular variant that was being applied to Philadelphia (what a great bit of casting!) but it was a form of restraint used in mental hospitals of that time. The patient was tightly bound in a sheet and soaked in ice water. Somehow this was supposed to have a calming effect.