RODENT TRAP
Tips the rat into a water tank, then resets itself.
A rat walks onto a runway inside a pivoted tunnel, and its weight rocks a pair of triangular plates that withdraw a latch bolt. A gate drops closed behind the rat, and the release of a latch rod allows the entire tunnel to swing downward. The rat slides off the runway and drops into a water tank in the lower chamber of the casing. A counterweight on a curved rod returns the tunnel to horizontal, relatching all parts for the next rat.
“Still further objects are to prevent the animal from reaching the bait provided for his enticement, and to provide free air passage through the entrance, so that the smell of the bait will be sensed throughout the length of said entrance.”— Walter Earl McKim, from the specification
And the world did not beat a path to his door.