- Lightweight, warm, and waterproof clothing. Getting one of three was possible. Maybe two of three. But all three? If it existed at all, you couldn't afford it.
- Comfortable backpack. As far as I can tell, the Romans used a sturdy forked stick which rested on the shoulder, and suspended their pack from the forked end. Illustrations from the crusades show a backpack consisting of a shapeless sack with shoulder straps. Overall, not as comfortable as today's form-fitting aerated backpacks.
- Matches. Have you ever tried to start a fire with flint and steel? It's not as easy as fantasy fiction makes it sound.
- A camp stove. Recent experience suggests that it takes a really long time to cook anything on a wood fire or hot coals.
- Well-preserved food. There were ways of preserving food: smoking, salting. You could make bread (sort-of) that lasted a while. None of it tasted good.
- Insect repellent. I'm still itching from a variety of bug bites. I can only imagine what it'd be like if I hadn't used bug repellent.
- Sunscreen. This might not have been as big a deal. Most people spent a lot of their time outdoors, and were likely pretty well tanned. And you can always wear long sleeves and hats if you weren't. But see above for the lack of lightweight clothing.
- Well-marked trail. There were actually such trails. They were called roads. The lack of a Park Service meant that any other trail you found couldn't be trusted to lead where you wanted it to, to be safe and manageable, or to always be well marked and easy to follow. Most folks stuck to trails they knew well.
And I'm sure I'm missing more. These are just the things I was glad we had during this trip.