(YouTube Link)
Sculptor Keith Newstead made this lovely brass pegasus automaton. He writes of its metal work:
As they had been cut from 1mm brass they were quite heavy and I was worried that the whole brass horse would be too heavy for the crank to lift it.
I made up the base , fitted all the parts of Pegasus together, fitted Pegasus to the base and joined up all the connecting wires.
As soon as I connected the wings I realised that because of the way they were set up they were actualy lifting the rest of Pegasus, in effect making it lighter.
http://www.keithnewsteadautomata.com/forsale/brass-pegasus and Link via Make
I don't see how the wings are operating in that way, but whatever...
I wanted to see the crank, too.
Technically, you're right. I believe what he meant, though, was that the wings were acting as a counterbalance, relieving some of the downward pressure on the mechanism -- in effect, you might say, making it lighter on the mechanics.
http://www.arthurganson.com/pages/Sculptures.html
Is it magic brass? If not, then no, it's not in ANY effect making it lighter.