Dan Brown's novel, The Da Vinci Code, claims that Leonardo da Vinci painted Mary Magdalene at Jesus' right hand in The Last Supper, as a clue that she was really Jesus' wife.
Wouldn't it be nice if we could interview Leonardo and ask him who it was he was painting on Jesus' right hand? Well, actually, we can!
During the years 1494-1495, Leonardo drew sketches in preparation for his famous painting, and wrote notes labeling them. We have those sketches to read.
Here is what Leonardo wrote about the three characters to the right of Jesus: "Another speaks into his neighbour’s ear and he, as he listens to him, turns towards him to lend an ear, while he holds a knife in one hand, and in the other the loaf half cut through by the knife. Another who has turned, holding a knife in his hand, upsets with his hand a glass on the table."
Notice that all three of these persons are described with the masculine pronoun. Can there be any doubt that da Vinci intended to paint Peter (the one who "speaks into his neighbour's ear"), Judas (the one who "turned, holding a knife in his hand," and John (the one who as "he listens to him, turns towards him to lend an ear")? The editor of the sketches notes that when Leonardo actually did the painting, he had an upset "salt cellar" rather than a glass, but otherwise he painted it as described. No Mary Magdalene. No "V." No "M." No secret codes.
(Source: Jean Paul Richter, The Notebooks of Leonardo da Vinci, 1880. On the Internet at http://www.fromoldbooks.org/Richter-NotebooksOfLeonardo/. Note the "contents" to the right and click on "X. Studies and Sketches..." Then click on each of the four pages that give da Vinci's words and the editor's comments of the sketches.)