What do George Washington, Albert Einstein and Stanley Ann Durham (Barack Obama's mother) have in common? Mormons have baptized each of them by proxy, performing a temple rite they believe gives human beings a posthumous opportunity to obtain salvation.

Researchers recently discovered that Mormons had similarly baptized the parents of famed Nazi hunter Simon Wiesenthal, whose mother died in a Nazi extermination camp in 1942. And one Mormon recently proposed for proxy baptism the still-living Holocaust survivor and Nobel Laureate...