the business proved lucrative, reflecting a rise in musical literacy during the period. The Whole Booke of Psalmes became the period's best-selling book and the standard English psalter of its time. Day's monopolies on these perennially popular works would be the basis of great wealth over the years and a good deal of conflict between him and his fellow stationers. In legal proceedings towards the end of Day's life, it was estimated that these particular patents were worth between £200 and £500 per year. Actes and Monuments In 1563, Day undertook the work for which he is best known, John Foxe's Actes and Monuments (also called The Book of Martyrs). Day and Foxe probably met through Cecil, and the two became close collaborators. Foxe was among those who seized on the advances in the printing trade as a tool for the spread of the Protestant Reformation. There is a tradition that Foxe, who revised and added material while the book was being set in type, actually lived at Day's shop at Aldersgate during the production of the book; he certainly received correspondence there and visited regularly. Day heavily invested time and money in the production of Foxe's book, the largest publishing project undertaken in England to that time, and he took an active part in the compilation of the material. Day used changes in type sizes or fonts to distinguish Foxe's editorial insertions from texts of his sources. The resulting lavish folio filled with woodcuts was an expensive luxury item, but it sold well and Day profited from his investment. Day continued to take on challenging and difficult projects. He had already printed the first English book of church music in 1560. In 1567, Matthew Parker, the Archbishop of Canterbury, commissioned Day to print a collection of writings attributed to the tenth-century Aelfric of Eynsham. For this work, Day, known for his fine and varied fonts, had the first-ever font of Anglo-Saxon type cut. The cost was borne by Parker, perhaps Day's most important patron. The font may have been designed by François Guyot, a French type-founder known to have worked for Day and lived in his household. Day used the same font to print Lambarde's Archaionomia (a collection of Anglo-Saxon laws) in 1568. In 1570, he printed Billingsley and Dee's English Euclid, which included folding and movable diagrams—one of the first printed books ever to do so. In the