According to an article on the REI Web site (http://m.rei.com/mt/www.rei.com/learn/expert-advice/ten-essentials.html) The Mountaineers came up with a list in the 1930's that was pointed to specific items, but the recent trend has been to working with systems:
● Navigation (map and compass)
● Sun protection (sunglasses and sunscreen)
● Insulation (extra clothing)
● Illumination (headlamp/flashlight)
● First-aid supplies
● Fire (waterproof matches/lighter/candles)
● Repair kit and tools
● Nutrition (extra food)
● Hydration (extra water)
● Emergency shelter
Easy enough to cover, but doing it in an ultralight way is a subject of debate equal to approving a Federal budget.
Here's my list:
Navigation: Green Trails maps and a Suunto MC-2G compass. There are suitable lighter compasses-- by an ounce or two. I think it should have adjustable declination and the mirror covers another category. Bottom line: compasses are not heavy, regardless of the model.
Sun protection: I wear sunglasses with bifocals for reading the maps and compass. I carry sunscreen in the smallest container suitable for the trip, not a big 6oz tube of the stuff. I also use bike gloves to protect my hands and a wide brim hat (Tilley T3).
Insulation: as light as a Power Stretch on up to a polyfill puffy per season and expected condtions. I usually have a little stuff sack with liner gloves, light beanie, spare socks and mid layer. I always have a windshirt and a ponch doubles for rain gear and emergency shelter.
Illumination: Olite i2 flashlight and Fenix HL21 headlamp. Both use one AA battery, so add one AA for a spare.
First Aid kit: AMK .3 with larger compresses, better tape and more meds.
Fire: mini firesteel, mini Bic lighter, a spy capsule with Tinder Quick tabs and a K&M match case with UCO storm matches and there is a button compass in the cap
Signalling: Fox 40 whistle, mirror on my compass, firesteel
Repair kit and tools: Victorinox Classic knife, Benchmade Griptilian 3.5" folding knife, flat pack of 18" duct tape, small roll 26 ga wire, hotel "freebie" sewing kit, small bundle light braided seine line, zip ties.
Nutrition: extra granola bar, hard candy
Hydration: 2 one liter drinking water bottles. Sawyer Squeeze filter and/or Micropur tabs. I keep a survival water bag in the crown of my Tilley.
Emergency shelter: poncho and AMK space blanket bivy and the line in my repair kit.
The flashlight, whistle, SAK Classic knife, spy capsule with tinder and firesteel are on a ring and carried in my pockets with the larger knife and the match case. The rest fit in a suff sack for quick locating and easy transfer from one pack to another.
Add training and improving skills and a can-do attitude, which are weightless.