Any information about sleeping in proper positions or firmness of mattresses? I know the Wabanaki peoples pre-colonization slept on firm ground on their side in a fetal position. I was told this keeps all your muscles stretched, and that hanging out in a squatting position also keeps your back and legs stretched. This seems to be true to me. Sometimes when I can sleep on my side, usually a back sleeper, I feel stretched and comforted but am wondering if there is any information on mattresses being bad? I assume as firm a mattress as possible is best.