Actors doing their own stunt work?

There are some shots in this film of the actors climbing around on some of the metallic beams of the Eiffel Tower. In the long shots, it is obvious that stunt doubles could be used. But in some of the close-up shots, when they're just perched still and not moving a great deal, it looks like the real actors. Could the production team actually persuade the actors to go and crouch still on a bit of the Eiffel Tower, then film them for a couple of seconds?? Would that be allowed... wouldn't insurance companies forbid that kind of thing? If anyone knows anything about the production history of this movie, I'd dearly love to know if the actors did any of their own "monkeying around", or how they made it look so convincing if it's fake?

There end it! (Jason Robards, Once Upon A Time In The West)