Harriot's 1631 book on algebra. Title page of 'Artis analyticae praxis' (1631), a work on algebra written by English mathematician and astronomer Thomas Harriot (1560-1621). It was published posthumously, as noted in the Latin text. At centre are the details of Hariot's patron, the Wizard Earl, Henry Percy (1564-1632), 9th Earl of Northumberland. Hariot also worked for Sir Walter Raleigh (as a mathematics tutor), travelled on an expedition to the Americas, worked on refraction, and carried out pioneering work in astronomy. The details of the London printer (Robert Barker) are at bottom.