An anvil is small, dense, and brutally heavy, commonly 100 to 500 pounds in a package the size of a toolbox. The whole game is respecting that weight so you move it without crushing a foot or your back.
Pro tip: Wear steel-toe boots and gloves; the number one anvil injury is dropping it on a foot.
Watch out: Never carry an anvil alone or by hand across any distance; a slip means a crushed foot or a serious back injury.