There were justifiable fears of being buried alive, before modern medicine could safely identify the difference between certain types of paralysis or coma and being dead. Fears which were exacerbated by fiction such as The Premature Burial by Edgar Allan Poe. As a result a bizarre range of contraptions were invented to signal having been buried alive, from bells, whistles and even a spring loaded ejector coffin which might actually kill other people from the shock of seeing an interred body spring out of the ground in a cemetery.Added to this were ranges of hermetically sealed iron coffins and a device to prevent grave robbing consisting of a booby-trap subterranean torpedo.For more of these, check out: http://deathreferencedesk.org/2010/02/02/premature-burial-device-patents/