i ownder if this is anything like a sensory deprivation tank. i did this onece. you entere a competely dark tank, and float in a saline solution, no sound, no light, almost no awareness of your body, as you are just floating in body temperature water. very interesting experience. you can travel anywhere in your mind you want ot go. it like letting go and falling deep into your own consciousness.
afterwards i was totally relaxed, i mean absolutely calm for several days. i would have loved to do it again, but never did. of course this is just for a short while, not the extended period of time you are talking about, but i think it involves some of the same things.