A few sleight-of-hand scholars (Penn & Teller among them) say the oldest known trick is the cup-and-balls, which was, they say, illustrated in the tomb of Baqet III and ostensibly described in an ancient Egyptian papyrus as performed by a magician named Dedi of Dejd-senefu.

Others say that's hooey, the Westcar Papyrus only has other feats of a more supernatural mode going on (Dedi reattaches severed heads) and the tomb really shows a game being played, not a magic trick. (Makes for a great backdrop for a re-enactment, though.)

The cup-and-balls (or praestigiatorum acetabula et calculi) is mentioned by Seneca the Younger in Epistle XLV, saying that the trick delights him until he can see how it's done.

That's within the first century CE.

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Edit to add: Oh, and there's also Glycon, who was a real god with real worshipers, who really appears on coins and in statues from the second century CE, but most what we know today comes from Lucian outing him as a hand puppet operated by an early ventriloquist.

Alan Moore, the comic-book writer who created V for Vendetta and Watchmen, has talked at length about how delighted he was when he realized he was being called to worship a hoax deity - there are excerpts of one of his books about his spiritual journey in this review .

There's a more academic overview of Glycon's weird history in an article in Fortean Times #276, written by Steve Moore (no relation).

Do you mean just anybody pretending to have magic powers, or specifically people doing performances for the purpose of entertainment?

(note: I am not qualified to answer either question, I'm just looking for clarification.)