Quotation from: The Notebooks of Leonardo Da Vinci
Written by: Leonardo da Vinci
OF THE LENGTH OF THE BODY OF THE GUN.
If you want it to throw a ball of stone, make the length of the gun
to be 6, or as much as 7 diameters of the ball; and if the ball is
to be of iron make it as much as 12 balls, and if the ball is to be
of lead, make it as much as 18 balls. I mean when the gun is to have
the mouth fitted to receive 600 lbs. of stone ball, and more.