Peniarth 6 is a set of four manuscript fragments, two of which contain the earliest Mabinogi text, dating to c. 1250. This is a century earlier than the oldest complete version of the Mabinogi, the Llyfr Gwyn Rhydderch manuscript, which dates to c. 1350.
In Peniarth 6 there is a Mabinogi passage from the Second Branch, and another from the Third Branch; as well as two passages of another story Gereint uab Erbin known today in The Mabinogion. The four fragments are conserved at Llyfrgell Genedlaethol Cymru, the National Library of Wales, in Aberystwyth; which also conserves Llyfr Gwyn. The third source of the Mabinogi text is a later MS. Llyfr Coch Hergest, conserved at Jesus College, Oxford; dated c. 1375-1425.
A complete transcription of Peniarth 6 fragments can be found here and can be downloaded as a .doc file; see reference details for this document and its editors below.
The summary descriptions which follow next, give the parallel text in modern forms.
Middle Welsh, modern typography: PKM 1951  Online text here: Williams cites Llyfr Gwyn pages.
Modern English translation: Ford, 2008 . Online text here.
Note, neither PKM nor Ford are giving a precise rendition of Peniarth 6; their works are from a composite of the three Mabinogi source manuscripts.
THE SECOND BRANCH FRAGMENT ‘Branwen uerch Lyr.’
This fragment, Peniarth 6i opens with Bendigeidfran in Ireland, making his famous statement, said to be proverbial in the text, that a leader must act as a bridge. So he makes his body into a bridge for his host to cross over. The Irish sue the British for peace, with Branwen as peacemaker. A huge guest hall is built for Bendigeidfran where the two peoples can meet in council. But Branwen’s distrustful and aggressive brother Efnysien realises there is treachery, so he crushes the hidden Irish warriors’ heads as the men crouch in hanging bags. The text stops short several lines before Efnysien’s englyn.
The excerpt corresponds to PKM pp. 40 -42 Middle Welsh, modernised typography. It begins at the bottom of PKM p. 40, extending to the end of p. 42. From PKM, the Llyfr Gwyn correspondence is most of page 52, all of 53, and most of 54.
The passage can be read in English translation, e.g. Ford, 1977 pp. 67 -68.
THE THIRD BRANCH FRAGMENT ‘Manawydan Uab Llyr.’
The fragment Peniarth 6ii begins after the four Dyfed royals have returned home from the family’s attempts at town life in English territory.
Manawydan and Pryderi set out to go hunting. Their hounds are enticed by a shining white boar which will not permit the dogs to reach it. The hunters are led to discover a marvel, a newly built tower of stone, never before seen. Manawydan warns Pryderi this is enchantment by the same agency which has devastated the whole land of Dyfed. But Pryderi is determined to save his hounds, and so becomes trapped in the tower.
It was poignant to me with my central interest in Rhiannon, to discover that this earliest fragment of the Mabinogi MSS. narrates her. Rhiannon gives one of her three famous rebukes. This one is to Manawydan her consort, for not trying to rescue his good friend Pryderi, her son. The fragment ends with Rhiannon sallying forth to save her son, and entering the enchanted tower. As soon as she is inside it she noticed … But to continue we must transfer to Llyfr Gwyn. Peniarth 6 leaves her transfixed at the sight she sees at the moment of recognising her son; his name does not appear but from context, as well as Llyfr Gwyn it is him that she sees.
The excerpt corresponds to PKM pp. 55-57 Middle Welsh, modernised typography. It begins at PKM p. 55, part way through para. 2. Note, the first part of the first word of the script is not extant, showing only ‘–ithyr’ of ‘odieithyr’ meaning ‘outside, without, beyond, above.’ (GPC ’oddieithyr’) The passage correspondence ends PKM p. 57, Para. 1, at end of line 2, before Pryderi’s name.
From PKM, the Llyfr Gwyn correspondence is the last part of page 69, all of 70, and the start of 71.
The passage can be read in modern English translation, e.g. Ford, 1977 pp. 79 -81. It begins p. 79, bottom of the page, last but one paragraph where the two men went ‘outside the court,’ and ends when Rhiannon enters the tower and sees …
A transcription of these Peniarth 6 fragments can be found here where it can be downloaded as a text file. It contains a lot of other material so scroll down using Edit/ Find on – Peniarth 6 -. For the two Branches fragments, locate – Peniarth 6i – and – Peniarth 6ii -.
REFERENCE: ‘13th Century Welsh prose manuscripts Version 1.0,‘ Trawsysgrifiwyd gan G. R. Isaac a Simon Rodway ac aildrefnwyd gan Silva Nurmio, Kit Kapphahn a Patrick Sims-Williams. (Transcribed by Simon Rodway and G. R. Isaac; edited by Silva Nurmio, Kit Kapphahn and Patrick Sims-Williams) Adran y Gymraeg, Prifysgol Aberystwyth, Dept. Welsh, University of Aberystwyth, 2010.
The Peniarth Collection NLW consists of 419 MSS collected by Robert Vaughan (1592-1666). Four fifths of these are his Vaughan library, which was known as the Hengwrt Collection until the 19thC. One fifth were added later from the Sebright and other collections. Robert Vaughan was held in such esteem he was known as ‘The Antiquary.’ (See a memoir by Robert Saunderson, 1834.)
Vaughan’s descendant Robert Williames Vaughan of Nanneu, Hengwrt, and Rug bequeathed his famous Hengwrt collection of MSS. including many of the most important Welsh language manuscripts extant, to his friend W.W.E. Wynne in in 1859. Wynne transferred the MSS to his Peniarth library that year. He studied the MSS., added notes on slips, publishing a Catalogue of the Hengwrt and Peniarth MSS, April 1861, Oct. 1869, April and Oct 1870, and April 1879. John Williams purchased the collection in 1904 so that when Vaughan’s son died in 1909, the manuscripts were transferred from Peniarth to the new National Library at Aberystwyth. This was a key foundation to the national library project. (NLW account here.)
Peniarth 6 was notably catalogued by J. Gwenogvryn Evans, Report on manuscripts in the Welsh language: Peniarth, vol. 1:3. London, 1905 which also catalogues Llyfr Gwyn. Further details are in Huws, Medieval Welsh Manuscripts, 2002 , and Rodway, Dating Medieval Welsh Literature, 2013.
I am indebted (March -April 2015) to Diana Luft, University of Cardiff for pointing me to the downloadable text file for Peniarth 6 text; and to Simon Rodway, University of Aberystwyth for clarifications on query.