Guys, I gotta tell ya, I really don't do PSK persay, in that I don't carry anything on me that remains static, is bare essentials, or has limited function. I gave up trying to come up with something small that would contain everything I might find essential at any given time.
What I did was got a messenger bag, put things in it I use everyday, added things I think I might need once in a while, and every so often change some contents to suit the conditions I may find myself in. I carry a small assortment of esstential OTH meds, along with any current scripts I need. I keep my wallet in it, my security badge for work, wire ties, string, floss, some duct tape, a compass, a lighter, some matches, a mylar bag shelter, an LED flashlight, some paper and some writing utensils, a couple condiment sized peanut butter containers, money, a needle and some thread. I keep a Leatherman, a penknife, another lighter, more money, my keys, another LED flashlight (photon style),my sunglasses, and a hankerchief on my person every day.
That's pretty much it. I may add one or two items or take something out occasionally (like my PDA or my GPS). Otherwise, I do fairly well. I work out of doors at remote locations in wilderness settings under isolated conditions, so I keep other supplies with me in vehicles I use. Since I am a communications specialist, I also keep a cell phone, a programmable uhf and a programmable vhf radio with me when I am away from the office. I also have a small HF transeiver that I can use to talk around the world on using only a 9 volt battery.
There are things you can do to improve your chances. If you think the mindset daily, the messenger bag is no big deal, and you learn how to deal without the stuff you can't take with you. I like to eat, and a couple tablespoons of peanut butter aren't going to break me, but will make my stomach be quiet for a while without depleting my body of water needed to digest it too much (digestion of food requires the use of a lot of the body's water). When I was doing escape and evade, water was always the big concern of the group, not food. The one time we did hunt together, we caught and tried to eat an Armadillo. It was the worst tasting piece of pork you could imagine, and even after doing without food for 4 days, I could only gag down 3 bites.
When we got back to base, those flattened peanut butter sandwiches looked so good, I couldn't open my mouth to say thank you when the mess cook handed me one because it was watering so much. I also couldn't quit drinking water for two days, and got sick twice from overdoing it.
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)