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.