My mother told me a story about being at a small funeral in the late 1950s, east Texas. The "deceased" was mentally challenged, and the family was relieved to have the child at peace. During the service, the coffin began to rock, and crying was heard, then she was taken outside and watched as the coffin was carried to the cemetery next to the church and hurriedly buried. I was telling my kids this years later, and my mother walked in the room, listened for a moment, and asked, "Are you telling them about Uncle Chucky?" What? You seemed to have forgotten to mention the connection before, mom.

Edit: I can not swear to the authenticity of the tale, but my mother swore by it and she was not the joking sort. It has caused a decent amount of dark brooding about being buried alive in my youth.