There are probably mystics living in the backwoods of the mountains in China where they still use abacuses (abaci?)
My dad had a prof in college that actually did have a "sliderule in his head" (those were is exact words). He could picture a sliderule exactly enough that he could move the slide back and forth to multiply numbers out and see what the logs were so that he didn't need to use a real sliderule.
My dad had a prof in college that actually did have a "sliderule in his head" (those were is exact words). He could picture a sliderule exactly enough that he could move the slide back and forth to multiply numbers out and see what the logs were so that he didn't need to use a real sliderule.