From "Winsor McCay and His Moving Pictures," 1906

McCay took an early interest in the capacity of the new medium of film to animate his cartoons--according to legend, when he observed his young son delighted by the moving pictures in a flipbook. But the creation of animated pictures was dauntingly labor-intensive--each frame had to be drawn separately, with incredible precision.
   The mind-blowing volume of work required to create an animated cartoon, treated comically, became itself the subject of McCay's first extended foray into the form. Here we see only the short moving picture that was the product of McCay's labors. It's still amazingly inventive, skilled work.