Before the projector became the means for film viewing, there was the Mutoscope.

Herman Casler, an American, invented this contraption in 1894. After dropping some coin in the slot and gazing inside (much like with the late 70s View-Master) a series of cards with pictures of a moving subject could be seen. A handle was turned which flipped the cards and made the subject appear to move.

Many of the early cards were of the mildly sexual variety. Women undressing, for example, was a popular theme ("By jove, that's an excellent corset"). Because of their proclivity for sporting a peeping Tom-like character, many Mutoscopes began to bare the inscription: "what the butler saw". Sometimes they were referred all together as "what the butler saw" machines.

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