Today's Now I Know by Dan Lewis is about a typo engraved in stone at the Lincoln Memorial (here is a link to the article). Essentially, when carving a copy of his second inaugural address into the marble, someone wrote EUTURE instead of FUTURE.

Are there any other examples of carved in stone typos like this? Places where what you're writing is meant to be permanent for everyone to see, so it's difficult to change what's been written, but you've accidentally made a typo.