This is from page 47.
Now, perform the envelope switch. The history of this move goes back to a gag used by Charlie Chaplin. It's contemporary use is based on a gypsy envelope switch used in a con game, but I've seen it used with forks by Banachek and know that mentalists such as Bob Cassidy use it.
He then goes on to describe the workings of Dr. Jacob Daley's Delight Switch.
Does this mean it should be credited to Charlie Chaplin?
I wonder what film it appears in?