The Poetic Edda is the modern attribution for an unnamed collection of Old Norse poems. Several versions exist, all consisting primarily of text from the Icelandic mediaeval manuscript known as the Codex Regius. The Codex Regius is arguably the most important extant source on Norse mythology and Germanic heroic legends, and from the early 19th century onwards has had a powerful influence on later Scandinavian literatures, not merely through the stories which it contains, but also through the visionary force and dramatic quality of many of the poems. It has also become an inspiring model for many later innovations in poetic meter, particularly in the Nordic languages, offering many varied examples of terse, stress-based metrical schemes working without any final rhyme, and instead using alliterative devices and strongly concentrated imagery. Poets who have acknowledged their debt to the Poetic Edda include Vilhelm Ekelund, August Strindberg, J.R.R. Tolkien, Ezra Pound, Jorge Luis Borges, and Karin Boye.