The very first mention of Journal of the Whills dates back to 1976. It was first mentioned in the original novelization of A New Hope (then called Star Wars: From the Adventures of Luke Skywalker.) In fact, almost the entire prologue is an excerpt from The First Saga of The Journal of the Whills, excepting a short quote attributed to “Leia of Alderaan, Senator.”
The entire prologue is too long to quote here, but details the decline of the Galactic Republic and the rise of the Empire. It likens the Republic to a strong tree able to withstand any outside attack, while the true threat was a rotten core.
It also includes an extremely concise summary of the political events detailed in The Phantom Menace, and provides our first glimpse of the Emperor.
“Aided and abetted by restless, power-hungry individuals within the government, and the massive organs of commerce, the ambitious Senator Palpatine caused himself to be elected President of the Republic. He promised to reunite the disaffected among the people and to restore the remembered glory of the Republic.”
It also contains this even more bare bones summarization of the political events. “Having exterminated through treachery and deception the Jedi Knights, guardians of justice in the galaxy, the Imperial governors and bureaucrats prepared to institute a reign of terror among the disheartened worlds of the galaxy.”
The prologue gives the impression that the entire telling of the whole Star Wars saga is just ancient moment in the the much longer history of the galaxy, or even the universe, at large. It is very much in keeping with the opening crawl line of “Along time ago, in a galaxy far, far away....”