Excavation is carried out by 26 workmen on two levels. The large machine has two crane booms mounted one above the other on the same vertical axis. The machine is mounted on wood tracks in the canal, and when pulled by a screw mechanism slides forward. The two crane booms function using the same rope, acting on the principle of counter-balance: the laborers work in teams so that when a bucket in the canal is full, another has already been emptied onto the embankment. The men on the embankment climb into the empty bucket which moves downward and by means of the counter-weight the rope in turn lifts the other filled bucket.
Codex Atlanticus, folios 3r, 4r (1503 - 1504)