Capitalization in Titles of Works

Q. A manuscript I’m working on right now features a quote in running text which refers to the twentieth century. Since the quote is from the New York Times, it says “20th century”—which does not match the number style for the rest of our book. Is spelling out the number a permissible change to the quote?

A. No, this is not the sort of thing you should change in a quotation. But don’t worry about appearing inconsistent; readers won’t hold you responsible. They understand that you weren’t available to copyedit everything that was ever written.