Lightest option I have ever seen was a small hammock slung between 2 trees. Would work in the PNW where there is no scarcity of trees to choose from. Could make it yourself, if you have access to a sewing machine. Use at least 1 inch wide straps to attach it to the tree, to prevent damage to the tree. Gathered end hammocks are quite easy to make. Photos off the internet to show different ways to sit in hammocks.
"I like this place and could willingly waste my time in it." Shakespeare
I just recently purchased the Sunyear chair. I like the tall back on it so you can actually sit back and relax . Total weight is 2.9lbs . I have used it about 5 times now and I really like it. I just strap it to the outside of my pack.
We always took 2 thermarest chair kits (the kind that use your sleeping pad) for the 4 of us. No one got to sit in one all the time, but everyone got a turn. They add a lot of insulation, so were good on cold mornings (or evenings) when the kids where having trouble keeping warm. The chair kit runs about 8 oz or less, and works with all sorts of of inflatable pads, as long as they are the right width (20").
I love my Alite Mayfly. It is one of the most lightweight chairs available, and is very comfortable. I bought it 3 or 4 years ago, and it has gone with me on every backpacking trip since. It is very low to the ground, which can make it a bit difficult to get up out of, but also means you can use it in the tent. This is one of my favorite pieces of gear I own.
I have walked myself into my best thoughts, and I know of no thought so burdensome that one cannot walk away from it. -Soren Kierkegaard