The Codex Manesse (Heidelberg, University Library, Cod. Pal. germ. 848) is a German manuscript, which was produced in Zürich between 1304 and 1340. It is an important literary manuscript, as it is the single most comprehensive source of Middle High German love songs, the songs of the minnesängers. There are 140 poets represented, who range in social status from the Emperor Henry VI to commoners. As important as the manuscript is for literary history, it is best known for its illuminations. There are 137 portraits of poets, many of them shown in full armor with heraldic devices. These illuminations have been widely reproduced, so much so that are almost the stereotype of High Medieval art. The last I was at Barnes and Noble I noticed at three books with cover art drawn from the Codex Manesse. The illustrations have also been widely used as decorative motifs. I have some wooden plaques with reproductions of some of these pages on my walls right now. Here are some of the images.
And, since this is a manuscript of songs, here is recreation of one of the songs.