The Lincoln Memorial has a typo on it that is still partially visible.

Two of Abraham Lincoln's most important speeches are carved on the inner walls of the Memorial: the Gettysburg Address on the north wall, and his Second Inaugural Address on the south wall. While carving the Second Inaugural Address, the engraver accidentally chiseled an 'E' instead of an 'F' in the word "future!"

The mistake was easily corrected by filling in the extra line, but the mistake is still quite visible if you look closely. By the way, Abraham Lincoln's body is not buried in the Lincoln Memorial. It's actually in Springfield, Illinois. And the position of the statue's hands are not sign language.