Stuff About Cards You Didn't Know And Probably Didn't Want To Know About by Jim Abrahams
The Lecture That Has Never Happened by Jim Abrahams Page 9 et seq.
Personal Comment: You need to talk as you perform this. But if you have the liberty and the people are relaxed enough for this sort of interlude it is a nice trick. And it works from a shuffled deck in use. What more can you ask for?