Thanks to the excellent scholarship of BARB, I've found the quotation about Mark Twain by Bret Harte in the Pemberton biography. It begins on page 73 and continues to the top of p. 75. The whole passage is well worth reading. According to Margaret Duckett's MARK TWAIN AND BRET HARTE, Harte told the story to Pemberton (p. 8). Everett Hooray for the Mark Twain Forum! Three Cheers for Barb!