The Percy Folio is a folio book of English ballads used by Thomas Percy to compile his Reliques of Ancient English Poetry. Although the manuscript itself was compiled in the 17th century, some of its material goes back well into the 12th century. It was the most important of the source documents used by Francis James Child for his 1883 collection The English and Scottish Popular Ballads.
The manuscript
Those who owned the manuscript before Percy did not treat it well; its owners had probably regarded its Middle English and border dialect as incomprehensible and worthless. When Percy first came across the manuscript, in the house of its former owner Humphrey Pitt at Shifnal, Shropshire, pages were being used by his housemaids to start fires. Percy had the manuscript bound, and the bookbinder inflicted additional damage in trimming the edges of the sheets, losing first or last lines on many pages. Percy did not treat the manuscript particularly well himself; he wrote notes and comments in it and tore out some pages after binding.
Percy's book was the constant companion of Gottfried August Bürger, a childhood hero of Novalis, one of the chief influences of George MacDonald, whom C.S. Lewis considered his master. And thus the manuscript, through Percy's book had a direct line of influence on Lewis's works.
Despite its losses, the Percy Folio ranks alongside the Exeter Book, the Pearl Manuscript, and the Cotton library's monstrarum librarum of the Beowulf manuscript as one of the most important documents in English poetry. A full edition of the folio's contents was not published until 1867, with a supplement of "loose and humorous" songs the following year.