Ancient necromancers preferred to summon spirits by sleeping directly on top of rotting human corpses

A closer look

If you want to chat with the dead, you apparently have to completely disregard all personal hygiene. Ancient Greek and Roman necromancers believed that spirits lingered near their rotting physical remains. To facilitate communication, practitioners would practice 'incubation,' a deeply disturbing ritual where they literally curled up and took a nap on top of a fresh corpse inside a dark tomb. The ensuing 'spiritual visions' were almost certainly just the result of inhaling massive amounts of toxic decomposition gases.