In this article I discuss an investigation of handwritten mathematics manuscripts known as navigation cyphering books. These manuscripts, which were prepared during the seventeenth and eighteenth centuries, are evidence of an educational tradition that was the primary means by which students in North America learned mathematics between 1607 and 1840. I examined the content, mathematical methods, and source material of two collections held in New England. Drawing on my analysis, I characterize a navigation cyphering book, discuss evidence of the implemented curriculum, outline relationships between manuscripts and printed textbooks, and consider the perspective cyphering books provide to modern mathematics education.