To what does Junpei compare solving the puzzle of escaping the sand hole in the novel, The Woman in the Dunes?

Junpei refers to Columbus’ egg when he has to solve the puzzle of escaping the sand hole. Columbus had a bottle with a wide body and a thin neck, and he wanted to get the egg into the bottle without breaking the egg, so he lit a match and heated the neck of the bottle, temporarily expanding the glass so the egg could pass through.