It was upon this date in the year 1497 that Fra Luca de Pacioli of the Seraphic Order of St. Francis, completed the text of the work by which he is best known to printers—De Divina Proportione, a treatise on the proportion of Roman letters. The original book was concerned purely with mathematical proportion and is considered by modern mathematicians to be more of a compilation of known theories than an original work. When it was finally printed in 1509 by Paganino de Paganini in Venice, the section dealing with the proportion of letters was added. Again, while this addition was not original, it is considered to be the first appearance in print of any work dealing with the mathematical formation of letters, and a forerunner of the later essays on the subject by Albrecht Dürer and Geofroy Tory, both of whom were undoubtedly inspired by the Franciscan Friar.

Luca de Pacioli was born in the town of Borgo San Sepolcro, where St. Francis had preached and lived for a period in the hermitage of Mont Casale, given to him by the people of the town. The religious order founded upon the memory of St. Francis was active in the town, and it was natural that when Luca and his two brothers decided upon theological careers that they join the brethren of the Franciscans. The order was noted for its scholars who enjoyed a wide reputation wherever learning was admired. Since Luca had intellectual aspirations, he found the brotherhood most congenial.

Prior to being ordained, Luca had been employed in a business house in Venice where he had learned accounting and had become intensely interested in mathematics, acquiring sufficient skill in that art to be able to tutor the sons of his employer. Shortly after becoming a Franciscan, he was ap pointed professor of mathematics at the University of Perugia, where he wrote a treatise on his subject. It remained unpublished, although the manuscript is still in existence in the Vatican Library. For the rest of his life he lectured in mathematics, becoming one of the noted authorities of his time, and enjoyed the patronage of a number of the important men of the period, including the Duke of Urbino. From time to time he returned to purely religious duties for his order.

In 1494 he published what is considered to be his masterpiece, Summa de Arithmetica, Geometria Proportioni et Proportionalita. This work is not considered to be important by modem mathematicians, except for those sections dealing with a system of double-entry bookkeeping, which are still being reprinted. While not the originator of the method, Fra Luca is considered to be the first person to teach it and write about it.