some day (not today, we're feeling too sick and at any rate we haven't worked out a method yet) I've decided to tackle the following challenge: calculate pi to at least twenty digits using a 5" Pickett pocket slide rule.
a slide rule (especially one that small) isn't good for more than about three digits of precision (if you're lucky) which means a painstaking process of successive approximation and work on paper. but it should be doable.
~Chara