Observe a demonstration of a Transverse Wave Machine from the Physical Science Collection at the Smithsonian's National Museum of American History. This instrument was manufactured in Germany around the turn of the 20th century. It is surprisingly small and can easily be held in one hand. It was designed to be placed in front of the lens of a projector and to be used for "shadow projection", which was a teaching method more common in Germany than in America. This machine only shows the sinuous motion of a transverse wave, but a more elaborate version was also made that included a series of angled rods that allowed it to also demonstrate longitudinal waves.
