The Five Negro Presidents: According to What White People Said They Were by J. A. Rogers

"If America hadn't already invented the 'one-drop rule' by this time, Rogers most probably would have. He seems to have had some sort of miscegenation-meter, which he used to 'out' all sorts of 'white' people as having black ancestry. And while he erred on the side of excess as he peered into the proverbial woodpile, Rogers got it right an impressive amount of the time, especially considering when he was publishing his work. (At the other end of his collected works, though, stands The Five Negro Presidents, which, shall we say, would get the Black History Wishful Thinking Prize, hands down, were there such in existence.)"―Henry Louis Gates, Jr., The Root