Opus Majus

Opus Majus was a book written by, obtained by Ezio Auditore da Firenze in the 16th century from one of Constantinople's many book shops.

Summary
''An exemplary specimen of overachievement, this massive books contains treatises on natural science, mathematics, grammar, physics, optics, and philosophy, to name a few. Written for Pope Clement IV as a summary of Bacon's achievements, the "Opus Majus" was evidently not terse enough for his Holiness, and was followed by Bacon's shorter "Opus Minus" just a year after. Whether or not this was later followed by the "Opus Pamphlet" has not been confirmed.''

Reference

 * Assassin's Creed: Revelations