The heaviest part guides motion; saw and arrow
A rule of motion with a mechanical saw and an arrow
A red-chalk note states a rule of motion: the heaviest part of any moving body guides its movement, the principle that makes an arrow fly point-first. At the top, drawn upside-down, is a mechanical saw carried on a frame; between it and the text is a small arrow that illustrates the rule.
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The heaviest part guides a moving body
Leonardo notes that the heaviest part of every moving body will be the guide of its movement, the reason a weighted point leads the flight of a projectile.
Mechanical saw on a frame
A reciprocating mechanical saw is sketched on its supporting frame, drawn inverted at the head of the leaf.
Arrow illustrating the rule of motion
A small arrow with a leaf-shaped head on its shaft is drawn as an example of a body whose heaviest part leads its movement.