Conjuring Credits

The Origins of Wonder

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Clocking the Deck

Clocking the deck is one of the oldest recorded card amusements. One of Leonardo da Vinci's contemporaries, Luca Pacioli, described the idea as Problem 21 in his Perugia manuscript (a.k.a. Vat. Lat. 3129), 1478.

It showed up in English in Thomas Johnson's Dainty Conceits, 1630, p. 10. In French, it was Problem XXXII in Chapter I of Jacques Ozanam's Récréations mathématiques et physiques, 1694. (See here for an English translation from 1708.) And Reinhard Müller has found the system in German in Natürliches Zauberbuch, 1745, p. 230. These all rely on the idea of canceling tens in the counting.

Friedrich Wilhelm Conradi gives an elaboration of the feat in his book Magisches Allerlei, 1903, p.102. He adds up the value and the suit at the same time, in two columns of numbers. He then expands the effect, letting a spectator call out any number and the performer names the card at that number.