Trick of the Mind Season 3 Episode 4

Derren: In 1883 a relatively unknown Italian magician and alchemist called Alessandro Donnini chose the streets of Venice for an incredible treasure hunt. He asked the count Giovanni Francesco to hide a necklace anywhere in the district of San Marco, and Alessandro's task was to find it. All of Venice was invited to watch and place their bets as to whether or not he could do it. Alessandro used a method called muscle reading. He had the count hold on to his wrist and felt for any tiny unconscious clues, as to which way to go. He found the necklace in just over an hour and a half. It was a triumph, and all the townsfolk went f*cking mental.