Here’s a possible timeline of that classical guitar passage that was under dispute at the Stairway to Heaven plagiarism trial:
 
Sonata di Chittarra, e Violino, con il suo Basso Continuo” by Giovanni Battista Granata (1659)

Video description: “Extremely similar to Led Zeppelin’s “Stairway to Heaven”; the arpeggio can be heard at 0:32 in this 17th Century Composition titled “Sonata di Chittarra, e Violino, con il suo Basso Continuo” by Giovanni Battista Granata.”

 
My Funny Valentine (from the 1937 Richard Rodgers and Lorenz Hart musical Babes in Arms)

The performers notice the similarity.
 
Taurus by Spirit (1968)

The relevant passage begins about 0:48 into the piece

Stairway to Heaven by Led Zeppelin (1971)

Is There Anybody Out There? by Pink Floyd (1979)

The classical guitar piece, which was allegedly contributed by producer Bob Ezrin, also bears a striking similarity to the passage in question, especially at the end.
 
My source for many of these pieces is an article from Guitar World,
“Five Songs That Sound Like Stairway to Heaven“. I don’t completely agree with the point the article is making: the issue wasn’t just a chord progression, but also a striking melodic similarity over that progression. Still, as you can hear from the above videos, variations on that melodic motif have been around for a long time. Another song referenced in the article, Davey Graham’s version of “Cry Me a River”, does use the same chord progression, but its melody is quite different. Still worth listening to, though!