This weekend I did something I haven't done in about 15 years. I spent an hour in a flotation tank. If you don't know about these, check out this news story featuring the place where I went:
Both times I found that it really does do all the things they promise. I was able to meditate very easily and deeply and when the hour was up, I felt incredibly relaxed and energized.
The next day, when I woke up my back and neck muscles, where I store much of my stress, were sore. Not in a strained kind of way, but the way they feel the day after you've had a really deep massage that releases lots of toxins.
I probably won't make the effort to do it again anytime soon, but I wouldn't hesitate to do it again. My shoulders are still hanging relaxed and lower than they have in months.