In modern-day sash windows, you might be a lot more likely to find a spring stability (or sash harmony) system. This is the spring-loaded unit which counters the power of gravity, in influence holding your sash window open with no need to have for cords, pulleys and people steel counterweights.  https://beautyproducts15814.thenerdsblog.com/41371730/helping-the-others-realize-the-advantages-of-sash-windows