It's important to measure your tension; we know this. I know on about this at length in my classes, and have talked about it on this blog.
And how do we measure tension? With a tension swatch, right. But that doesn't eliminate the need for a sanity check once in a while.
I'm distracting myself with what was supposed to be a quick and easy project: Matador, in Noro Iro.
(You may find it startling that there's a Noro yarn I hadn't yet worked with -- I did.)
Anyway, I carefully measured my tension, and I was absolutely correct. So why on earth is the thing a good 4 inches wider than it's supposed to be? Stuff happens, I know that. This is a good and humbling reminder that it's useful to measure a second time -- once you've started working.
They call it a sanity check, I think, because its goal is to preserve your sanity.
It's a seriously great yarn, though.