In the 1850s, Robert-Houdin presented a new experiment in his Soirées Fantastiques theater: second sight. Robert-Houdin's young son sits blindfolded on stage, while his father asks the audience to bring out various objects that are personal to them. Despite being blindfolded, the son was able to guess and detail the borrowed objects with precision, and the experiment was a success.
However, in 1849, a certain Mr. F. A. Gandon published a book entitled: La seconde vue dévoilée, dernier coup porté aux sorciers et aux sortilèges, Ouvrage entièrement nouveau, donnant à tout le monde la facilité de faire des expériences dites de Seconde-Vue ou de Double-Vue. This book is said to contain the secret verbal code that Robert-Houdin would use in his séances to communicate information about the object he was holding to his son!
But Robert-Houdin had more than one trick up his sleeve. He improved the act, and soon presented a completely new version: with a bell! Here, the magician never utters a single word, and simply warns his son that he's holding an object by the tinkling of a little bell. That's all there is to it. The blindfolded son, still deprived of his sight and without a word from his father, always manages to describe the spectator's object in great detail. It's a miracle that Gandon's book fails to explain, just as today's magic historians still have many doubts about the method used!
I never knew so many details! THANK YOU