The question of cleanliness is one every age and culture has answered with confidence. For the first-century Roman, being clean meant a two-hour soak in baths of various temperatures, scraping the body with a miniature rake, and a final application of oil. For the aristocratic Frenchman in the seventeenth century, it meant changing your shirt once a day and perhaps going so far as to dip your hands in some water. Did Napoleon know something we didn't...