Now, I've just come across a great reference to "the world's oldest apocalypse prediction":
"Our earth is degenerate in these latter days. There are signs that the world is speedily coming to an end. Bribery and corruption are common."
- Assyrian clay tablet, circa 2800BC
This reference is sourced to Isaac Asimov's Book of Facts. The problem is, I can't substantiate it. I don't have a copy of the Book of Facts handy and, even if I did, I would need to know more about the clay tablet in question before I could trust Mr Asimov's word on this.
So if I were to use this quote in any sort of serious discussion, I would need to accompany it with a shot of skeptical "penicillin". I would have to make my friends aware that I could not stake my life on the it being accurate. This would be boring and long-winded.
The only alternative is to try to track down the tablet in question online. This is not proving easy: googling for the translated text just finds thousands of people who have quite clearly copied it straight out of the Book of Facts. This is not corroboration.
So I need to dig deeper. With a bit of effort, I'll be able to figure out how the Assyrian research community organises its information, which should give me some idea of where to find this particular tablet. So far I've come across the Cuneiform Digital Library Initiative (not so helpful as it doesn't give translations) and the Neo-Assyrian Text Corpus Project (which appears to be defunct).
Beyond that, I may have to gatecrash the local university library. Watch this space.
It may take a while to learn the truth here. Heck, I might actually need to learn Assyrian to track down the tablet (or to demonstrate that it probably doesn't exist). I am unlikely to go that far. But the time I do spend on this exercise will be time well used - a tithe spent on improving the information available to the community as a whole.