True weight of gym pulley systems

So I have a 200 lb stack on my pulley. Then there is a 17.6 lb piece on top that has weight horns for adding free weights. As we all know pulleys exist to make moving heavy things easier. What is the most accurate way of measuring this? I'm thinking of a analog scale with hooks on each end that hunters use to weigh their dead dear. Maybe there's something overlooked to this idea. I'm pretty sure it has to be accurate but I thought I'd check just in case, science can be a funny thing. If not give me your ideas.