From Brian Hook[0], who worked with John Carmack at id Software:

> I remember Carmack talking about productivity measurement. While working he would play a CD, and if he was not being productive, he'd pause the CD player. This meant any time someone came into his office to ask him a question or he checked email he'd pause the CD player. He'd then measure his output for the day by how many times he played the CD (or something like that -- maybe it was how far he got down into his CD stack). I distinctly remember him saying "So if I get up to go to the bathroom, I pause the player".

> You know what's pretty hardcore? Thinking that going to the bathroom is essentially the same as fucking off.

0: http://bookofhook.blogspot.com/2013/03/smart-guy-productivit...