For those doing a retreat that has a sweat lodge be very careful. It seems some of these spiritual gurus don't quite get the whole safety thing and have too many people, a poorly designed sweat lodge, or rocks that, when heated, release poison gas. Strangely, the poor folks around here (ND) seem to have no problems, but the expensive retreats somehow screw it up every couple of years. I guess that's the difference that apprenticeship give you.