Selected Leaves of Codex Gigas, A 148, unknown creator, unknown location, undated via National Library of Sweden, Creative Commons Attribution 4.0 International License.
“The Codex Gigas or the Devil’s Bible at the National Library in Stockholm is famous for two features. First, it is reputed to be the biggest surviving European manuscript. (Codex Gigas means ‘giant book’.) Secondly, it contains a large, full page portrait of the Devil.” - National Library of Sweden
If you get excited by Pythagorean based ancient Greek music theory then LJS 47 in the manuscript for you! Written in France in 1490 the text reflects an older (10th-century) tradition and the numerous diagrams related to ratio and pitch demonstrate later developments in the tradition. Fols. 24r and 25v depict examples of those diagrams.