In the video below, Peter Reveen speaks about the illusion, and if I'm not mistaken, Julie Eng has a cameo as well!
From the Walter Zaney Blaney YouTube channel:
The history of the famous Ladder Levitation Illusion as told by Walter Blaney himself. Guest appearance by David Copperfield, Lance Burton, James Dimmare, Jeff McBride, Peter Reveen, Steve Dacri and Stan Allen. A chapter in the documentary series Still Zaney After All These Years.
[via Carey Lauder and Ryan Joyce]