It doesn't take much digging to find sources older than that, really. ;) For instance, you can check out my own post about it at http://www.clevcode.org/cicada-3301/, originally written mid-January 2012. The oldest comment on the post is from 2012-01-14. There were articles written about this back in 2012 as well btw.
PS. I'm the Joel Eriksson that was interviewed for the article in question.
The primes in question = 509, 503 and 3301. 509 and 503 was the width and height of the image. Obviously, you don't get a new prime after multiplying these numbers together though. ;) For those who don't find this immediately obvious, keep in mind the definition of a prime ...
Well, he obviously has misunderstood both TOR and the definition of a darknet. The surface web _is_ just the tip of the iceberg though, but that's because it's defined as the part of the web being indexed by public search engines.
Your private Facebook posts, your Gmail inbox, private Dropbox files, and so on, are all parts of the so called deep web according to this definition. Due to this, it's not a very meaningful concept, and says absolutely nothing about the size of any "human-trafficking rings, black market drug markets and terrorist networks".
PS. I'm the Joel Eriksson that Chris interviewed for the article in question, and for anyone who would like more detailed and less sensationalist information about the Cicada 3301 stuff, feel free to read my writeup at http://www.clevcode.org/cicada-3301/. :)
PS. I'm the Joel Eriksson that was interviewed for the article in question.