Before Benjamin Franklin became a printer, newsman, author, inventor, philosopher, diplomat and founding father of the United States, he failed math twice.

In 1715, Franklin’s money-conscious father removed his young son from the Boston grammar school that might have led to a college education and sent him to learn writing and arithmetic in preparation for a printing apprenticeship. As Franklin later recalled, he “acquired fair writing pretty soon, but I failed in the arithmetic and made no progress in it.”

By age 16, “being on some occasion made ashamed of my ignorance in figures, which I had twice failed in learning when at school,” Franklin continued, “I took Cocker’s book of arithmetic and went through the whole by myself with great ease.”

This brief account of the statesman’s mathematical education is a well-known digression in Franklin’s autobiography. Few authors have failed to spot the irony in one of the 18th century’s most recognizable polymaths struggling with basic number skills. Yet the story of the “book of arithmetic” that finally helped Franklin master the subject is little known today—another irony, because in his day, it was every bit as famous as he was.

Cocker’s Arithmetick was probably the most successful elementary math textbook published in English before the 19th century. It epitomized an age in which the expanding worlds of commerce and capitalism, education and Enlightenment, coalesced to make basic arithmetic the classroom staple it is today. In many ways, the story of its success mirrors that of the man whose face now adorns the $100 bill.