It’s become a bit of a tradition amongst math personalities on the internet to, on pi day (March 14th), go to ridiculous lengths to calculate pi by hand. Sometimes this means measuring the period of a pi-endulem, sometimes weighing a cardboard cutout of a circle. I’ve even see people do cartwheels. The rules are simple: calculate pi. No calculators allowed. Bonus points for originality and ridiculousness.

This is of course a riot of fun, and I always participate, but I can’t help but feel there’s another mathematical constant left out.

e, defined below, is a heavyweight math constant. Second only to pi, it is one of the most well-know and widely-used (amongst math people anyway).