You have that slide rule in the back of the closet. Maybe it was from your college days. Maybe it was your Dad’s. Honestly. Do you know how to use it? Really? All the scales? That’s what we thought.

While some (math-phobics) still may relish the simple beauty and non-threatening functionality of the abacus, there are those who have made the transition to more challenging computing gadgets—many ...

Used by engineers for centuries, they were displaced by pocket calculators and all but forgotten until Mr. Shawlee created a subculture of obsessives and cornered the market. By Alex Traub For about ...