The Oxford Canonicianus miscellaneus 47 is an autograph codex by its author in a small-size cursive script with an accurate hand not lacking of a certain elegance. The work is a compendium of a lost much wider treatise. The colophon on f. 219v records the occurrence of the work’s completion on Sunday, February 29th 1440 in Udine by the medical officer Giovanni Fontana. The work, which is dedicated to Domenico Bragadin, Paolo della Pergola’s successor as a mathematics lecturer at St. Marks’ School of Venice, describes a tool for trigonometric measuring that could be considered as a sextant prototype: the ‘trigonum balistarium’, or arbalest-shaped triangle. On ff. 1-13r the author describes its construction to the last detail and gives an accurate pen-made drawing for any phase thereof. On the following pages there are proof demonstrations, each of which endowed with pen-made drawings, of the varied uses of the tool that would later find its main application in overseas navigation. Beyond its geniality and extraordinary precision, another surprising element is the terminology used to indicate lines, intersection points, angle measurements, mathematical operations with expressions and ways that are more alike the current use and therefore it also seems strange that although the author had dealt with and worked out such a matter in such an early period, he has nevertheless remained nearly unknown until present days.
A critical partial edition (with German translation and about 175 coloured diagrams) edited by Horst Kranz:
De trigono balistario – Das Ballistendreieck. Technische Kapitel und ausgewählte Anwendungen. Texterstellung, Übersetzung und Zeichnungen, ed. Horst Kranz (s.l., 2021)