Is Pure White (255/255/255) really possible?

I have gotten into the 250's on all three, but I have never gotten pure white. I even tried just lighting my pure white paper with 16 35w's and it still wasn't pure white (Manual: f3.5, ISO100, 1/60th, WB: 5000).

This makes me think there has to be a problem with my settings.

Halp?