The Japanese have a particular obsession with sleeping low. Some claim it's the result of an ancient belief that evil spirits dwell in the air above the human head, and that sleeping low keeps you safe. In Japan, the highest point of the house is the living room, where the hearth used to be; the low point is the bedrooms. The height of the Japanese bed frame was originally the height of the futon mattress, so that you could roll it up during the day and use it for sitting or kneeling during the day.