The National Archive of Holland has a Flickr account, and one of the albums documents dozens of antique inventions from around the world. These run the gamut from ingenious to pretty nutty.

Using bicycle tubes as swimming aids, Germany, 1925.

A monowheel motorcycle that could reportedly hit 150 KPH (93 MPH), invented by Italian M. Goventosa de Udine, 1931.

The "Cyclomer" amphibious bicycle, France, 1932.

This all-terrain vehicle could reportedly "descend slopes up to 65 degrees." England, 1936. Reminds me of the more recent Brazilian boomerang suspension truck.

A pram (baby carriage) with an antenna, radio and loudspeaker to keep the kid quiet. USA, 1921.

Wooden bathing suits, "supposed to make swimming a lot easier." Washington State, USA, 1929.

Early wearables: A radio built into a straw hat. USA, 1931.

"Extensible caravan, built by a French engineer." France, 1934. I can't imagine what the application is, and I have a hard time believing this thing has a single axle.

A piano designed for the bedridden. Great Britain, 1935.

"Hamblin glasses," a pair of (I assume) periscope-style spectacles for reading in bed while keeping your head comfortably reclined. England, 1936.

This is one of the more intriguing ones, with a frustrating lack of details: "Electrically heated vest, developed for the traffic police in the United States. The power is supplied by electric contacts in the street. Location unknown, 1932."

Human version of a cow-catcher, here placed on a car for "reducing the number of casualties among pedestrians." I.e. the guy in the photo isn't riding it, he's demonstrating what supposedly happens when the car strikes a pedestrian. Paris, 1924.

A primitive trip computer. The pace of the automatically scrolling "map" is keyed to the rotation of the car's tires. Location unknown, 1932.

A portable bridge for emergencies. Invented by someone named L. Deth, the bridge collapses down to something that can be transported in a pushcart. Netherlands, 1926.

A sort of personal, wearable boat for fishing. Netherlands, 1915.

Wirelessly transmitted newspaper. "Photo shows children reading the children's page of a Missouri paper," 1938.

Anti-flu masks? Nope: "Plastic face protection from snowstorms." Montreal, Canada, 1939.

A gas-resistant pram (baby carriage) for wartime. England, 1938.

Way ahead of its time: A Colt .38 revolver with a camera that automatically snaps a photo when you pull the trigger. New York, 1938.

I think I got all of the good ones, but there's more to see here.

Also note that they've got an album called Moustaches.