Heimskringla

Heimskringla was a book written by, obtained by Ezio Auditore da Firenze in the 16th century in Constantinople.

Summary
''A thirteenth-century Old Norse saga composed by Icelandic scholar Snorri Sturlson. Though told with a richness and energy that gives its tales a level of realism unusual for the time, most scholars believe that most of the "Heimskringla" is built on a foundation of well-intended but ultimately invented speculation.''

Source

 * Assassin's Creed: Revelations