Is there a photo of Mark Twain on the tiber river in rome

I have a large (about 20”x20”), late 19th century, photograph of a man in a white suit, standing in a small skiff with a boy, and another man fishing. The standing man looks a lot like mark twain. The skiff is on the tiber in front of the castle of st. Angelo with st. Peters in the distance. I bought the framed photo in 1975 from a small flea market in georgetown, washington, d.c. I’ve always wondered if it really was mark twain.