From A Connecticut Yankee In King Arthur's Court, Mark Twain:

Intellectual 'work' is misnamed; it is a pleasure, a dissipation, and is its own reward. The poorest paid architect, engineer, general, author, sculptor, painter, lecturer, advocate, legislator, actor, preacher, singer, is constructively in heaven when he is at work; and as for the magician with the fiddle-bow in his hand, who sits in the midst of a great orchestra with the ebbing and flowing tides of divine sound washing over him - why, certainly he is at work, if you wish to call it that, but lord, it's a sarcasm just the same. The law of work does seem utterly unfair - but there it is, and nothing can change it: the higher the pay in enjoyment the worker gets out of it, the higher shall be his pay in cash, also. And it's also the very law of those transparent swindles, transmissible nobility and kingship.