In this explanation Robert-Houdin is entirely wrong. The real secret of lying on top of a sharp-edged razor, sword, or sabre rests on the fact that the performer does actually lie upon it in a perfectly motionless position. Were he to move but the width of a hair, backward or forward or sidewise, the weapon would slice his body, resulting in instant death or horrible mutilation. I have watched cheap performers of this class of work, in dime museums or fairs, walk up a ladder of sharp swords which I had previously held in my hand. They would place the foot down with infinite precision and then press it into place. This position will not result in cutting, but let the performer slip or slide and the flesh would be cut instantly. I have also seen an acrobat, working in a circus, select two razors in first-class condition, place them on a socket with the edges of the razors uppermost, and with his bare hands he would do what is known as a hand-stand on the keen edges of the blades. This trick of absolute balance is acquired by persistent practice from youth up. Again Robert-Houdin errs wofully in comparing the sabre-swallower to the swallower of broken bottle-heels and stones. Sabre-swallowing is one trick, swallowing pebbles and broken glass belongs in quite a different class. And when I say this I do not mean powdered glass, but pieces of glass first broken, then chewed, and finally swallowed. On page 426 Robert-Houdin puts the two tricks in the same class, as follows: "When the trick of swallowing bottle-heels and pebbles was to be done, the Aïssaoua really put them in his mouth, but I believe, I may say certainly, that he removed them at the moment when he placed his head in the folds of the Mokadem's burnous. However, had he swallowed them, there would have been nothing wonderful about this, when we compare it with what was done some thirty years back in France by a mountebank called 'the Sabre-Swallower.' "This man, who performed in the streets, threw back his head so as to form a straight line with his throat, and really thrust down his gullet a sabre, of which only the hilt remained outside his mouth. "He also swallowed an egg without cracking it, or even nails and pebbles, which he caused to resound, by striking his stomach with his fist. "These tricks were the result of a peculiar formation in the mountebank's throat, but, if he had lived among the Aïssaoua, he would have assuredly been the leading man of the company." The sabre-swallower never releases his hold on the weapon. The pebble and bottle-heel swallower does--but brings them up again, by a system of retching which results from long practice. The Japanese have an egg-swallowing trick in which they swallow either small-sized ivory balls or eggs, and reproduce them by a retching so unnoticeable that they could easily show the mouth empty.