The original "Think" Pad
More proof it wasn't our idea first...
Back before PDAs or other fancy organizational IBM provided "Think" pads to their employees. They were encouraged to use them to take notes as they went through their day to keep organized.
IBM stopped making them, so they're hard to find these days. I got this one from my father. I used it until I passed through my Moleskine and HipsterPDA phases.