This engraving by Durer plays an important role in Dan Brown's new novel - the lost symbols. The symbols here are a magic square in the right top corner of the drawing. If you click on the picture, you can see that the numbers 1 to 16 are organized in such a way that every row or column sums up to 34, even if you divide the square in 4 smaller squares - the sum of that square is 34 again - sweet! Unfortunately Dan's book isn't that great. Professor Landon is over and out I am afraid!