I agree with pretty much everything Mister Squishy said about Rosetta Stoned. I think it's easily the best song from 10,000 Days and definitely one of Tool's best. To take it at face value and write it off as a silly song about aliens seems to be a huge mistake. Sure, the lyrical content might not be as complex or 'serious' (for lack of a better word) as the rest of Tool's catalog, but I don't think it's simply a song about hallucinogens and aliens. Like any work of art, it's meant to be taken as a metaphor. Tool's other music is usually a complex metaphor for something more simple. I think Rosetta Stoned is unique in the fact that it's a simple metaphor (not simple meaning it's easy to decipher, but simple meaning the way in which the metaphor is articulated isn't as complex as Tool's other lyrical content) for something more serious.

Or maybe we're just over-thinking it and it's really about one of the guys doing DMT and a recollection of his trip. Either way, it's a fucking rocking song. Lyrics aside, the musicianship on that song is beautiful.