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counting frame
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John Napier introduced a system called "Napiers Bones," made from horn, bone or ivory the device allowed the capability of multiplying by adding numbers and dividing by subtracting.
John Napier dies -
mechanical coculator
Plan projects on a visual timeline
Map milestones, phases, deadlines, and key events in one place so the sequence is easier to see and share. Timetoast is a timeline maker for work, school, research, and stories.