"A Mule will be a Mule."

"It is sometimes amusing to observe the athletic wagoner hurrying an animal to its post--to see him heave upon the halter of a stubborn mule, while the brute as obstinately sets back, determined not to move a peg 'til his own good pleasure thinks it proper to do so--his whole manner seeming to say, "Wait till your hurry's over!" I have seen a driver hitch a harnessed animal to the halter and haul his mulishness forward, while each of his feet would leave a furrow behind until at last the perplexed master would wrathfully exclaim, "A mule will be a mule any way you can fix it."
--Josiah Gregg, Commerce of the Prairies, 1844