I wouldn't have thought to take apart a simple water boiler (at least not in recent years) so that was enlightening. Sometimes simple but functional designs can be fascinating, after getting to used to doing less with more (arduinos on everything) rather than more with less (completely mechanical control systems).

I have a zojirushi, but only with three temperature settings. Maybe I should mod it to fully variable... although I really want to make a teapot with a built in thermometer more than anything. The water heater wouldn't cool fast enough to really make the variable temp worth it.