HockeyDad
Lil-Rokslider
I use a old wool blanket at the bottom of my pack, then load in a 40# bag of water softener salt. Makes it compact yet carries well.
Like some of the guys who use water, I use a similar method. I fill up several 100 oz bladders with beer. When I get to the top, I drink all the beer. It really saves on my knees on the way down.