Various models and solutions to the crowded chessboard puzzle from 1917
The crowded chessboard is a 100 year old problem appearing as problem 306 in Dudeney's book "Amusement in Mathematics".
Quoting from the book: "The puzzle is to rearrange the fifty-one pieces on the chessboard so that no queen shall attack another queen, no rook attack another rook, no bishop attack another bishop, and no knight attack another knight. No notice is to be taken of the intervention of pieces of another type from that under consideration - that is, two queens will be considered to attack one another although there may be, say, a rook, a bishop, and a knight between them. And so with the rooks and bishops. It is not difficult to dispose of each type of piece separately; the difficulty comes in when you have to find room for all the arrangements on the board simultaneously."