Peter Ramus (1515–1572) was a French humanist, educator, and mathematician who wrote books on arithmetic and geometry. In 1580, a volume containing his work in both arithmetic and geometry was published in Basel as *Arithmeticae libri duo: Geometriae septem* *et* *viginti*. The title page of this book is shown above.

On page 75, Ramus provided a diagram illustrating the sighting of a cannon employing a cross-staff.

On page 77, examples are given of the use of a cross-staff in determining the unknown height of a tower and the depth of a well.

Some further illustrations from Ramus’s *Way to Geometry* follow.

Pages 290–291 discuss the properties of cones and cylinders.

Pages 274–275 provide insights into the Platonic solids.

Pages 268–269 consider the volume of rectangular prisms.

*These images from its George Arthur Plimpton Collection are presented through the courtesy of the Columbia University Libraries. *

For related works by Ramus from the Columbia University Libraries, see images from another edition of his *Arithmetices libri duo* (1586; original 1555) and from a 1636 edition of his *Way to Geometry*.