Surprise Appearance
Image: Wikimedia Commons

“Eight complete perfect dovetail shuffles, breaking pack exactly in center; that is, cutting off just 26 cards each time and dropping cards from each half alternately, brings the pack to its original order.”

— T. Nelson Downs, in a letter to fellow magician Edward G. “Tex” McGuire, 1923

11/14/2016 UPDATE: Sid Hollander and Harold VanAken sent this demonstration:

eight shuffles

Here’s what it looks like in the hands of a skilled shuffler (thanks to reader Sascha Müller):