My first rule of shopping for a lightweight backpack is to eliminate all of those 3 pounds or heavier. However, if you’re really serious about being lightweight, you should probably set you upper limit at 2 pounds. There are many, many choices out there in this range, including the GoLite Race Pack.
Don't be put off by pack names such as "adventure pack" or "race pack" because it is mainly marketing jibberish.
I like several things about this pack: it weighs 1 pound, 8 ounces, costs less than $100 and has plenty of pockets, including a big pocket for rain stuff, a wet tent or whatever.
In addition, it has side pockets for water bottles. However, if you don't want to carry water bottles, there is an internal pocket to carry a hydration bag with up to 3 liters of water. The water bottle pockets can be used for other items.
With all the minimalist gear you'll be carrying, the GoLite Race Pack with 2700 cu in + 400 cu in for the lid will be plenty of space for everything you need to carry.
There also is a mesh back panel to keep sweating down. A light pack is your base for going lightweight and 1.5 pounds for one of your major pieces of gear is a good start.
Be safe. Be light. Be one with the pack.