This is the most common advice I've found in my research on walking the Camino de Santiago. The accepted wisdom is that your pack should be no more than 10% of your body weight. For the duration of my pilgrimage, I'll have nothing except what I carry with me or buy en route.
As a bare minimum, this means carrying a sleeping bag, a complete change of clothing, a towel, and rain gear. Add to that personal toiletries, a pair of Crocs, flashlight, spare batteries, battery charger and spare battery for my camera, extra memory cards, water bottle (1 litre of water weighs 1 kg), packets of instant oatmeal (48 g per packet), waterproof matches, a candle, first aid supplies, multi-vitamins, gloves, extra-large garbage bag, multi-tool, pocket New Testament and prayer book, small diptych icon, maps and a guide book -- well, it adds up quickly!
Right now, my pack is slightly less than the desired 10%. I'm also kinda chubby, so perhaps I should be packing according to some mythic "ideal body weight." Or should I use my lean body mass, which is actually higher than the standard BMI table recommends for my height? (Right now I'm weighing in at 109 kg, which is almost 2.5 kg less than when the fast began on November 15.)
Anyway, I'm looking for ways to shave weight from the load which I will be carrying on my back for about 800 km. I know that there will be some sort of village or town about every 10 km along the route. Do I really need to carry 480 g of instant oatmeal? Sure, that is a great breakfast at any time and especially while winter hiking, but wouldn't I be better off relying on the network of hostels and refuges which run the length of the Camino?
Let's look at my first aid supplies. I probably won't need anything more than regular sized bandages for blisters, perhaps a small tube of antiseptic ointment. I can buy ibuprofen if I start to ache too badly, and if I actually do run into a situation where I need the abdominal bandage or the 10 cm x 10 cm sterile gauze pads, I'll probably be in such bad shape I won't be able to use them anyway.
The Boy Scout motto is "Be Prepared," and I usually am. But the Camino is different. For one thing, although I'll be doing some hiking through some beautiful country, I'll have hot showers and a clean bed every night. I'm not going on a back-country expedition. If I need something, I can buy it.
"Be Prepared." It's a great slogan, especially for someone with delusions of self-sufficiency. Yet even as a Boy Scout, you are part of a troop. On a pilgrimage, the last thing one ought to do is try to be self-sufficient. That is spiritual cancer.
A common experience related by people who have walked the Camino de Santiago is that "the Camino provides." Whether it is a friendly smile just when a pilgrim is in the throes of despair, or a fellow hiker who appears out of nowhere and sets you on the correct path only to vanish again moments later, part of the lore of the Camino is that no pilgrim is walking alone.
How much do I need to bring with me? Or how much should I rely on Providence? I hope that part of my pilgrimage will entail shedding some of the unnecessary baggage which has been weighing me down for years.
Come to Me, all you who labor and are heavy laden, and I will give you rest. Take My yoke upon you and learn from Me, for I am gentle and lowly in heart, and you will find rest for your souls. For My yoke is easy and My burden is light.