What do you write in your logbook after you've just piloted a rocketplane past the "sound barrier" for the first time? If you're Chuck Yeager, you keep it short: "#1 ok"
That's the notation (then) Captain Yeager made in the Flight and Engineering Report for Bell XS-1 Ship #1 (serial no. 6062), aka "Glamorous Glennis," on this day in 1947, right after he'd flown faster than Mach 1 for the first time in recorded history. The flight, over the desert in Muroc, California, lasted just 15 minutes.
Click here to see a scan of Yeager's report for that day, and here to read about other famous logbooks.
Or watch below as Yeager explains (in a 1953 press conference) how it felt to fly supersonic.