Sir Isaac Newton's Notes, Before the Discovery of Gravity.
Was walking through town today when an interesting thing happened: I tripped over a stone and fell down. Not up. Down. I contemplated this as I stood and dusted myself off. “Did you see that?” I said to the nearest witness, a homely wench by the alley. “I fell down.” “Yes,” she said, “and looked a fool doing it. Never have I seen a man fall so clumsily.” I suppressed the urge to call the woman on her stupidity; I went ‘round the corner where I tripped myself several times. And each time, I fell down. Query: Have I ever fallen up? Trying to jog my memory …

After that letter to Optimus Prime, more hilarity from McSweeney’s. Too funny.