The Williamson Aeroplane Camera doesn't have a propeller so that it can fly. Users of this World War I-era camera would attach it to the bottom of a plane. During flight, the movement of the propeller advances the film.
This is only one of twelve unusual antique cameras which you can find at the link. The others include a camera hidden in a cane and another that could be carried by a pigeon.
Link -via David Thompson | Photo: George Eastman House