A ball rebounding within a circle: the gentlest percussion
A ball b strikes at point m, returns to it, and inflicts the least injury by contact
A note on percussion states that a ball b striking at the point m returns to that same point and never leaves contact with the circle until its impetus is spent. Leonardo adds that this kind of impact does the least injury to the place that receives it through contact. A large circle is traced across the upper half of the sheet, with a straight line at the left carrying the lettered marks the text refers to, illustrating the ball's circular path.
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A ball returns to its point of percussion
If the ball b strikes at the point m it returns to m and never departs from contact with the circle until its impetus is consumed. Leonardo adds that this quality of percussion inflicts the least injury on the place that receives it by contact.
Circle and the line of the figure
A large circle is drawn across the upper half of the sheet, with a straight line set to its left carrying lettered marks. It provides the geometric setting for the ball's circular path described in the note below.