Arthur Ainslie, Water Wizardry: A collection of tricks in which water is the chief agent
“ The weak point of the trick is at the beginning; only one bowl is shown to be empty. Is it not possible that some of the very attentive members of your audience will notice this fact and will say to themselves: "He showed us only one empty bowl—wonder what's in the other?" Of course, people ought not to think in this way, and some conjurers believe that they do not, but my experience tells me that there are always some persons in every audience who do not miss much when it comes to judging a trick and trying to find out the method of the conjurer. ”
