A perpetual-motion scheme from Henry Dircks’ Perpetuum Mobile (1861). Each bellows is fitted with a weight and filled with quicksilver, and a canal connects each opposing pair of bellows. Thus the weights will continually compress the bellows on the left and expand those on the right, forcing the quicksilver always into the rightmost bellows and ensuring that the wheel turns forever. Won’t they?

Future civilizations will remember us for one thing: We finally found a way to keep the cereal from getting soggy.

This “crispy cereal serving piece and method,” patented by Alton Davis in 1991, connects two bowls with a chute. “A measured, quickly consumable portion of the cereal can then be urged with a spoon or other eating utensil from the upper bowl down the chute and into the milk, from where it can be consumed before it absorbs sufficient quantities of milk to become soggy.”

Take that, Phoenicians!

Patented in 1991, Frederick Sevilla’s helium-filled sun shade combines protection with effortless portability.

It must be tricky to manage, though — one slip and you’ll never see it again.

Joe Armstrong’s 2000 patent application is a model of clarity:

“The amusement apparatus is operated by one user for self-kicking the user’s buttocks, or an alternative embodiment allows one user to operate the crank while a second person positions himself to receive a paddling of his buttocks for entertainment of observers.”

He adds that an LCD can display kicks per minute, and the whole apparatus can be folded for storage. Kudos.

Broke and lazy? With Chris Michaels’ “TV control device,” patented in 1976, you can change the television channel from the comfort of your armchair — and it’s “considerably less expensive than its electrical and electronic counterparts.”

The trouble is that you’ll need to find a TV with knobs.

Martin Goetze’s 1896 “device for producing dimples,” left, was uncomfortably similar to a hand drill — an ivory knob was placed on the site and a rotating cylinder made the surrounding skin “malleable.”

Evangeline Gilbert’s improvement, right, patented in 1926, was essentially a headpiece that drove depressions into the cheeks. “The length of time on this pressure will vary with different persons, but it has been found that, if the appliance be used during the night, dimples will be present during the next day.”

Baltasar Gracian wrote, “Beauty and folly are generally companions.”

In 1971, Fred E. Stuart patented a “firearm mounted in a shoe heel.” He envisions military personnel and police using it when “regular weapons have been lost or become jammed.”

The shoes can fire regular bullets, frangible projectiles, or even tear gas, and can be fitted with multiple barrels that fire independently.

Combine this with a reversible sole and you have the makings of a perfect murder — a concealed weapon that confuses the crime scene.