A little-known fact about William Tell is that apart from being an expert with the crossbow, he was also an accomplished chef. One day he had prepared a new dish for his Swiss friends but, ever the perfectionist, he felt there was something missing from the sauce. "Do you think the sauce needs more berries?" he suggested. "No, no," they said. "I think you have just the right amount of berries." "More salt, then?" "No, the amount of salt is perfect," they insisted. "Herbs, that's it," he said tri…