I remember the elders in our family telling when I was a child that only sleeping with head northwards is prohibited, because doing so will bring the wrath of Lord Yama on the perpetrator.
In fact, I also remember that only when a person actually dies, then the dead body used to be placed on the floor at home with head placed intentionally northwards. Before the dead body is carried away to the smashaanam all the household members prostrate to Lord Yama southwards, while prostration southwards is strictly banned on all auspicious occasions. Many of the kriyas associated with death, shraddham, tharpanam etc.involve activities usually the exact opposite of those which are to be done during auspicious rituals. For example, yajnopaveetham which is normally worn on the left shoulder is reversed and worn on the right shoulder as pracheenaveethi during shraddham, tharpanam and other apara kriyas. Parishechanam which is done clockwise on auspicious occasions, is done anticlockwise by the shraddhakarta on their plaintain leaves on which food is served to pithruvarnam.