Inspired by GLE's UPG getting ripped off and presented as fact, here are some examples from very early sagas of in-text source attributions, context setting, and disclaimers of the possible inadequacy of the author's knowledge, to demonstrate that this has always been important.
I'll start by reminding you that Snorri quotes 345 verses of poetry in Skáldskaparmál alone, for things as simple as "Óðinn is called Allfather" (attributed to Arnórr jarlaskáld), and almost all of them are attributed either to author or poem title when no author is known.
Snorri Sturluson, Heimskringla (from Snerpa, translation mine):
Í bók þessi lét eg rita fornar frásagnir um höfðingja þá er ríki hafa haft á Norðurlöndum og á danska tungu hafa mælt, svo sem eg hefi heyrt fróða menn segja, svo og nokkurar kynkvíslir þeirra eftir því sem mér hefir kennt verið. Sumt það er finnst í langfeðgatali því er konungar hafa rakið kyn sitt eða aðrir stórættaðir menn, en sumt er ritað eftir fornum kvæðum eða söguljóðum er menn hafa haft til skemmtanar sér. En þó að vér vitum ei sannindi á því þá vitum vér dæmi til þess að gamlir fræðimenn hafa slíkt fyrir satt haft.
‘In this book I had written old accounts of those rulers who have held kingdoms in the northern lands and have spoken the Danish tongue, as I have heard wise men tell, and their lineages as I have been taught them. Some of this is found in genealogies in which kings or other noble men trace their lineages, and some are written from old poems or narrative songs with which men have entertained themselves. Although we can never know what truth there is in them, we know that old wise men have considered them true.’
Ari fróði, Íslendingabók (from Heimskringla.no, translation by Siân Grønlie, 2006)
Íslendingabók gerða ek fyrst byskupum órum, Þorláki ok Katli, ok sýndak bæði þeim ok Sæmundi presti. En með því at þeim líkaði svá at hafa eða þar við auka, þá skrifaða ek þessa of it sama far fyr útan áttartölu ok konunga ævi, ok jókk því, er mér varð síðan kunnara ok nú er gerr sagt á þessi en á þeiri. En hvatki er missagt er í fræðum þessum, þá er skylt at hafa þat heldr, er sannara reynist.
‘I first wrote the Book of the Icelanders for our bishops Þorlákr and Ketill, and I showed it both to them and to the priest Sæmundr. And in so far as it pleased them to keep it as it was or to add to it, I wrote this on the same subject, besides the genealogies and regnal years of kings, and I added what has since become better known to me and is now more fully reported in this book than in the other. But whatever is incorrectly stated in these records, it is one’s duty to prefer what proves to be more accurate.’
Yngvars saga víðförla (from Snerpa, translation by Hermann Pálsson and Paul Edwards. 1989. Vikings in Russia: Yngvar's Saga and Eymund's Saga):
En þessa sögu höfum vér heyrt ok ritat eptir forsögn þeirar bækr, at Oddr munkr inn fróði hafði gera látit at forsögn fróðra manna, þeira er hann segir sjálfr í bréfi sínu, því er hann sendi Jóni Loptssyni ok Gizuri Hallssyni. En þeir, er vita þykkjast innvirðuligar, auki við, þar sem nú þykkir á skorta. Þessa sögu segist Oddr munkr heyrt hafa segja þann prest, er Ísleifr hét, ok annan Glúm Þorgeirsson, ok inn þriði hefir Þórir heitit. Af þeira frásögn hafði hann þat, er honum þótti merkiligast. En Ísleifr sagðist heyrt hafa Yngvars sögu af einum kaupmanni, en sá kveðst hafa numit hana í hirð Svíakonungs. Glúmr hafði numit at föður sínum, en Þórir hafði numit af Klökku Sámssyni, en Klakka hafði heyrt segja ina fyrri frændr sína.
‘We have heard this story told, but in writing it down we have followed a book composed by the learned monk Odd, which he based on the authority of well-informed people mentioned by him in his letter to Jon Loftsson and Gizur Hallson. Those who believe they know better must augment the account wherever they think it wanting. The monk Odd says he heard this story told by a priest caled Isleif, and also by someone called Glum Thorgeirsson, and he had a third informant named Thorir. Odd took from each of these whatever he thought most interesting. Isleif told him that he had heared this story from a certain trader who claimed to have heard it at the royal court of Sweden. Glum had the story from his father, Thorir from Klakka Samsson, while Klakka learnt it from his older kinsmen.’
Sverris saga (from a composite of attestations), translation by J. Stephton, 1899):
Here we begin to speak of events which happened a while ago, within the memory of the men who related them for this book; to speak, that is, of King Sverri, son of King Sigurd Haraldsson. The beginning of the book is written according to the one that Abbot Karl Jonsson first wrote when King Sverri himself sat over him and settled what he should write. [...] The latter part of the book is written according to the relation of those who remembered what happened, having actually seen or heard it, and some of them had been with King Sverri in battles. Some of these stories were fixed in memory, having been written down directly the events occurred, and they have not been altered since. Possibly, if this book is seen by those who have full knowledge of the events, they may think many matters passed over hastily, and many left untold which they regard as worthy of mention; they may well cause these to be written down if they wish. And though, in telling o[f] battles against large numbers, some things are here said to have occurred otherwise than seems most probable, let all know of a certainty that nothing has been added. To us it seems probable that the stories are true which are told in books concerning famous men who lived in old times.
