Via First Time User.  I wondered whether this was actually rideable, but found a video of a 12-foot unicycle being propelled.

This set of 110-year-old condoms, made from the swim bladders of fish, are up for auction in Vienna. Delightfully, they seem to have been meant to be reusable, as evidenced by the former owner's careful tally of how many times each condom had been used. It looks as though you were only supposed to reuse 10 times.The tally 10/9/8/7... is faintly visible on the red lining of the box, magnified here.Discovery credit to Dinosaurs and Robots, via BoingBoing.