In the Chinese province of Fu-Kein, people called on their ancestors for dream revelation by sleeping on graves
This also happens in Indonesia. It is a practice called (sp?) Semanyat. Former President Gus Dur Wahid used to order his ministers to go to graveyards in the middle of the night, sleep on the tombs of their ancestors, and report back to him what their dreams were like. From this he would apparently glean information about how to run the country.