1600~1699: English Woman’s Fiery Death
Sometime in the 17th century, an elderly woman was found burned to death in her cottage in southeastern England. Other than the woman, nothing else in the cottage was damaged; not even the bedclothes (sheets) on which she lay. An observer was quoted as saying: "No man knoweth what this doth portend." There were suggestions that it was divine retribution for an unknown sin.
The account above is from Reader's Digest Strange Stories, Amazing Facts, and they don't give a source for it. Given the extremely vague nature of this story, I'll be lucky to recognize it if I see it in another book... and until I find more details, it's totally unconfirmable.