Fiction In The Past

Poul Anderson's time travel fiction, including his Time Patrol series, presents authentic-seeming accounts of past ages but also projects a lot of historical fiction and science fiction into the past:

in the fourth century, Ulfilas, Christian missionary to the Goths, met the mysterious Wanderer, the source of some of the Eddaic stories about Odin;

in Berlin in 1858, two Time Patrolmen watched a holographic recording of the meeting;

one of the Patrolmen, Carl Farness, was the Wanderer but Carl thinks -

"Was it truly me looming over [Ulfilas], lean, gray, cloaked, doomed and resigned to foreknowldge - yon figure out of darkness and the wind? On this night, one and a half thousand years after that night, I felt as if it were somebody else, Wodan indeed, the forever homeless."
-Poul Anderson, "The Sorrow of Odin the Goth" IN Anderson, Time Patrol (Riverdale, NY, 2006), pp. 333-465 AT 1858, p. 403.

And when the Roman general Cerialis makes peace with the Northern rebels, their intermediary is another Patrolman, Everardus/Manse Everard.