I determined that there is an error in Gutenberg's version of Samuel Butler's prose translation of the Iliad, where somewhere in the catalog of ships Homer's tessarakonta is translated as something other than forty. I think it was fifty.

I briefly looked into the process for correcting Project Gutenberg, but didn't do anything. And I have no idea whether the error was made by Butler (and would appear in print) or by whoever transcribed Butler's work for Project Gutenberg. I would argue that in either case Gutenberg should correct the text, but I can see where opinions might differ if the error is original to Butler.