Tom Miller wrote:

I had a Physics Prof that use to do calculations in the blackboard, then get
one of us in the class to work out the figures with a slide rule while he
mentally calculated the answer. He was an eccentric old chap and while he
calculated he wiggled his hand in a circular motion,sometimes clockwise
,sometimes counter clockwise. Turned out he had used a mechanical
calculating machine during the war and still mentally twisted his hand
forward or back according to whether he was multiplying or dividing.



Ah Ha ! a Curta operator. :-)
...lew...