Light lunch

Wang Gongfu, of Lianyungang, China, eats glass twice a week. He ate his first glass cup when he was 20 and in the intervening 22 years he has eaten more than 440 lb (200 kg) of glass. His favourite is teacup glass, but he is also quite partial to electric lightbulbs.

The risks associated with eating and swallowing glass depend on its size, shape, and sharpness, jagged pieces being far more dangerous than smooth. The human digestive tract can cope with many things - including bones in meat or fish - so small pieces of glass can travel right through the bowel and be passed out normally.

Sword swallowers must first eliminate the gag reflex, which they do by putting their fingers, then spoons, knitting needles, and eventually wire coat hangers down their throat. They must also relax their Pharynx, esophagus and the muscles of their neck, and make sure that the world is lined up perfectly. Another trick of the trade is to lubricate the sword beforehand with either saliva or butter.