You’ve successfully tested the limits of how much can fit into a #10 envelope without bursting its seams, but now you’re questioning how much postage you need. Sure you could just slap a few of the new 44-cent stamps onto whatever you're sending and be done with it, but that’s good money you’re throwing away.
Instead, spend just a few bucks now to build a simple magnetic postage scale, newly updated from an original article in the February 1971 issue of Popular Science.
This handy little device works by balancing the unknown weight (your obese letter) against a calibrated opposing force developed by five or six small ring magnets poled to repel each other.
Go ahead and make your own!
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.