Modern Magic: A Practical Treatise on the Art of Conjuring

The first rule to be borne in mind by the aspirant is this: “Never tell your audience beforehand what you are going to do.” If you do so, you at once give their vigilance the direction which it is most necessary to avoid, and increase tenfold the chances of detection. We will give an illustration. There is a very good trick (which will be described at length hereafter) in which the performer, after borrowing a handkerchief, gives it to some one to hold. When it is returned, it proves to be torn into small pieces. It is again handed to the holder, who is instructed, in order to restore it, to rub it in a particular manner; but when again unfolded, it is found in a long strip. These effects are produced by successive adroit substitutions, and the whole magic of the trick consists in the concealment of the particular moment at which each substitution is effected. Now, if you were to announce to the audience beforehand that you were about to cause the handkerchief to appear in several pieces, or in a long strip, they would at once conjecture that the trick depended on an exchange, and their whole vigilance being directed to discover the moment of that exchange, you would find it all but impossible to perform the trick without detection. If, on the other hand, you merely roll up the handkerchief, and ask some one to hold it, the audience, not knowing what you are about to do, have no reason to suspect that you have handed him a substitute; and when the transformation is exhibited, the opportunity of detection will have already passed away.