Icelandic historian, poet, and politician Snorri Sturluson (1179-1241) wrote what we today often refer to as the Prose Edda (or Younger Edda, or even Snorri’s Edda) in the early 13th Century. It is one of our major sources for Norse mythology, as well as a textbook in the art of poetry.

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Codex Upsaliensis (DG 11). Originating from around 1300-1325, it’s the oldest surviving manuscript of Snorri’s Edda. It is held at the Uppsala University in Sweden.
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Codex Regius (GKS 2367 4°) A manuscript of Snorri’s Edda written in the first half of the 14th century. Currently held by Árni Magnússon Institute for Icelandic Studies in Reykjavík. Here’s an online digital scan.
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Codex Wormianus (AM 242 fol) A manuscript of Snorri’s Edda written in the mid-14th century. This one is now at the University of Copenhagen. The National and University Library of Iceland has a great web site with scans of this codex, physical descriptions, and historical data on the manuscript. It tells us that Ole Worm owned the manuscript after 1628, and this is why it is now called Codex Wormianus. Ole Worm was professor in medicine at the University of Copenhagen, and also helped establish the scientific study of Nordic antiquities and runes. Here’s from University of Copenhagen’s website: “Unlike most Icelandic parchment manuscripts, the leaves in the Codex Wormianus are strikingly pale. The explanation is that Worm had his Icelandic assistant wash them in old urine, or so Worm says in a letter to [his friend, historian Stephan] Stephanius, who had asked him how he could make his dark brown manuscript of Grettis saga more legible.” The website of The National and University Library of Iceland has more info on this: “Sveinn Jónsson (1603-87) cleaned the manuscript with urine, with the result that the chapter headings and many marginalia and initials vanished or became illegible.” …so, that’s a word of warning there, if you were thinking of pissing on your library in order to clean up some books.
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Codex Trajectinus (MSS 1374) A manuscript of Snorri’s Edda that was made in the second half of the 16th century. It is kept in the library of the University of Utrecht, Netherlands. Here’s an online digital scan.