An orbicular pyramid equal to a rectilinear figure
A cone reduced to a straight-line triangle, algebraic ratios, and spinning-top studies
Between two parallels Leonardo draws two rectilinear triangles and an 'orbicular pyramid' (a cone), arguing that a cone diminishing in equal proportion is equal to a figure of straight lines that begins and ends with it. A column of cosa (algebraic) notation at the right works with doubled and multiplied quantities. Spiral figures of a spinning top and whip, together with a spoked wheel, are drawn but not transcribed, and further untranscribed writing stands at the upper right.
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An orbicular pyramid (cone) equal to a rectilinear figure
Two rectilinear triangles and an 'orbicular pyramid' are set between two parallels. Leonardo argues that the pyramid diminishing with equal proportion, though orbicular (a cone), is equal to a figure of straight lines that begins and ends together with it.
Algebraic (cosa) notation of ratios
A column at the right sets out cosa notation, the medieval shorthand for the unknown quantity, arranged in the doubled, quadrupled and higher ratios the sheet is catalogued under. Values such as 10, 1, 7 and 8 are combined against the abbreviation 'co'.
Spinning top and whip
Several tight spiral figures and a spoked wheel depict the motion of a spinning top (trottola) driven by a whip (frusta). These are drawn but carry no transcribed caption; further untranscribed writing appears at the upper right.