I used an egg sinker with a wire through it. I left about 6 or 8" stick out of both ends. One end I bent a loop in to tie the line too. A wire clothes hanger was just the right diameter to fit through. I sort of bent a dog leg in it so the sinker would stay about midway on the wire. It didn't hang up easy and I could tell if the bottom was gravel or soft mud or clay and could feel it "tick" brush and logs and rocks and things.You just got a feel for it.
Back before you had all these things to rely on you got better at doing things with the old eyes and brains and simple tools. Sort of like shooting a rifle with open sights and a bow by instinct alone.