I believe, at some point, Wikipedia was talking about partnering with Archive.org to turn all their citation links into Wayback Machine snapshots—including the ones for journal PDFs.
Presuming such a thing ever gets done, an archival copy of Wikipedia + the Wayback Machine pages Wikipedia references would then make a pretty good "sum total of all human knowledge."
There's a lot that's not written down. Didn't NASA try to coax Apollo engineers out of retirement for their new big space stuff? The engineers had knowledge that wasn't written down, wasn't accessible, or was simply lost.
Sure, with sufficient time you could recreate the knowledge with brand new engineers but you'd be rediscovering lost information.
Presuming such a thing ever gets done, an archival copy of Wikipedia + the Wayback Machine pages Wikipedia references would then make a pretty good "sum total of all human knowledge."