Even back in the 80's I was doing multi-day hikes with a simple day-pack of basic stuff. I knew I wasn't the only one, and I certainly wasn't the first.
In the 50's, as hiking for pleasure was becoming more popular and mainstream, packs carried by many were already approaching levels between 30lb and 60lb, especially for long-distance treks such as the Appalachian Trail in the USA. (European equivalent trails were slow in coming), but it was the 'AT' that Emma 'Grandma' Gatewood hiked end-to-end, with "a duffel bag containing an army blanket, a plastic sheet, and other very simple gear". She became, and still is, a legend.
Even before this, outdoorsman Horace Kephart, in 1917, had written on the subject of reducing the load, allowing a hiker to go further, faster, and easier. Ultimately the practice of ultralight hiking goes back even before soldiers in armies across the centuries, and before explorers in unknown lands.
It really began with nomadic tribesmen, natives across the world who were in tune with their surroundings to such an extent that they would find everything they needed along the way: food, shelter, clothing, first aid, weaponry, and entertainment. From the Aborigines and Maori of Australasia to the Sami tribes of Scandinavia, the Bantu and Masai tribes of Africa, those of South America and all over the world, natives knew how to travel.
There are, to my mind, two approaches to Ultralight: the technical and the cultural. Between the two extremes, each hiker finds their own way.
Just imagine, after a confortable lunch stop, leaning back against a tree beside a stream, nervously contemplating the struggle to once again lift the heavy pack that you were so glad to dump on the ground just a short while ago. It looks much like the boulder its leant against.
Now your vision blurs, and then clears, and suddenly your pack has gone, and in its place is a small bag that you would have overlooked had you not been seeking it. You lift it with just two fingers, lightly flick it over one shoulder, and make your way onwards.
Admit it - sounds good, doesn't it?