This would require moving a million tons of earth, and Leonardo calculated the man-hours necessary by doing a detailed time-and-motion study, one of the first in history. He figured out everything from the weight of one shovel-load of dirt {twenty-five pounds} to how many shovel-loads would fill a wheelbarrow {twenty}. His answer: it would take approximately 1.3 million man-hours, or 540 men working 100 days, to dig the Arno diversion ditch.
( Walter Isaacson )
[ Leonardo da Vinci ]
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