Last time I checked, parchment was the most durable medium mankind ever used on a regular basis.

I find it an interesting question to ponder what we consider worthwhile retaining for more than 2000 years (from my personal library, perhaps just the Bible, TAOCP, SICP, GEB and Feynman's physics lectures and some Bach organ scores).

EDIT: PS: Among the things "Show HN" has not yet seen is a RasPi based parchment printer...

It would be an interesting project to create an entire archive of books of HN discussions and preserve them for hundreds of years for archivists to explore. I hope they find this comment.