If he had been a great and wise philosopher, like the writer of this book, he would now have comprehended that Work consists of whatever a body is obliged to do, and 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 drive four-horse passenger-coaches twenty or thirty miles on a daily line, in the summer, because the privilege costs them considerable money; but if they were offered wages for the service, that would turn it into work, and then they would resign.
Mark Twain, The Adventures of Tom Sawyer