Here is a near-perfect film version of the urban legend. I think it demonstrates that this tale still stands the test of time. Like all good horror it is ancient and simple and brutal.
Just go into the bathroom and say the words... and see what happens.
The Premature Burial (1962) Pressbook - Ray Milland, Hazel Court, and directed by Roger Corman: what's not to love? Here's the comic book reader version: Download Premature Burial Pressbook