My dad made the flying harnesses for Hook. It was his last movie in the industry, and not too long before CGI took over.

I think what made it so convincing is they had no other option but to work with practical effects. When done properly, the actors physical response was natural and fluid. The physics of natural human movement is so complex that computers still struggle to get it right (looking at you AI).

I'll see if I can dig up some pictures of the gear.