The (eventually) two Nalgenes is all the water I want to carry on a day hike. I do, however, need to put some water in the truck. Goes on the list - thanks for reminding me.

I also have a canteen that I can strap on, but I am loathe to carry any more weight - although, in hot weather (a rarity in Maine), I wouldn't need some of the clothing. Would still net out heavier than any such tradeoff would allow. I have actually hiked all day with just a bottle of Gatorade.