ANIMAL TRAP
A small trap whose only purpose is to fire a larger trap.
A large pair of spring-closed outer jaws is held open by a latch and latch-keeper, temporarily secured by a safety ring on a chain while a smaller trap is set between them. Once set, the inner trap's own jaw takes over holding the latch-keeper, and the ring is removed. The mouse tilts the bait-plate; the trigger releases the inner jaws, which snap on a leg and simultaneously free the latch-keeper. The outer jaws then close on the body of the animal.
“The primary object of the invention is the provision of jointly operated dual traps which are designed respectively to catch a leg of the victim as well as the body of the animal, in order to prevent its escape.”— Leonard C. Johnson, from the specification
And the world did not beat a path to his door.