Modern Magic: A Practical Treatise on the Art of Conjuring

[C] When the number named is more than half the total number of the pack, i.e., more than 16 in a piquet pack, or more than 26 in a whist pack, it is quicker, and has precisely the same effect, to count off the difference between that and the total number from the top, and place them at the bottom. Thus, in a piquet pack, if the number called be 12, you would count off 12 from the bottom, and place them on the top; but if the number called were 24 you would achieve the same object by counting 8 from the top, and passing them to the bottom. In all tricks which depend on the naming of a card drawn or thought of, it adds greatly to the effect to have the card named before you turn it up. This trick, unlike most, will bear repetition; but it is well on a second performance to vary it a little. Thus you may on the second occasion say, when the card has been thought of, “I will choose for myself this time; your card will appear at number 30.” It is desirable to name a number very near the total number of the pack (which we are now supposing to be a piquet pack), as the difference between that and the total number being very small, it is easy to see at a glance the number of cards representing such difference, and pass them to the bottom of the pack. You take in this instance two cards only, that being the difference between 30 and 32, and pass them to the bottom, when the card will, as you have announced, be the thirtieth.