"He had discovered a great law of human action, without knowing it - namely, that in order to make a man or a boy covet a thing, it is only necessary to make the thing difficult to attain. If he had been a great and wise philosopher, like the writer of this book, he would have comprehended that work consists of whatever a body is obliged to do, and that play consists of whatever a body is not obliged to do. And this would help him to understand why constructing artificial flowers or performing on a treadmill is work, whilst rolling nine-pins or climbing Mont Blanc is only amusement. There are wealthy gentlemen in England who drives four-horse passenger-coaches twenty or thirty miles on a daily line in the summer, because the privelege costs them considerable money; but if they were offered wages for the service, that would turn it into work, and they would resign."
The Adventures of Tom Sawyer