There's a story I recall about some famous and brilliant mathematician — perhaps Norbert Wiener — who rarely took his
nose out of a book and who didn't like to waste time: he would read while walking to and from the classroom (or perhaps his office) but have his arm
out such that with a small part
of his (very big) brain he could count the doorframes as they were
ticked off against his hand; at the right count, his wrist would stiffen, and with his arm as a lever, rotate himself into the room still reading.