**Puzzle 66**

@DanOneata
Where did the definition of the relation \\(\le_{X \times X}\\) in the product preorder come from?

$$ x \le_X x' \text{ and } y \le_X y' = (x, y) \le_{X \times X} (x', y') $$

Is it just an alternate formulation of the "pixie dust"?