I not only want a horse to stand and "whoa" while the line or reins are dangling, but I also want him to "whoa" if I fall off or the saddle comes off or both...so I do things a bit differently than most...and I start them young. Once the horse leads well and is dependable, I will toss a saddle up on him...no cinch and no latigo. Then I'll lead him around with it, if it falls off, I'll give him a sharp "whoa" and stand there till he calms down (if he spooked), if he didn't, I'll praise him and simply stand there for a few seconds. Then I'll put the saddle back up and we'll keep doing that until the saddle falls off and he doesn't move. If the saddle doesn't fall off and I want it too, I'll reach up, grab the stirrup and pull it off. Once he's comfy with the saddle falling off and standing quietly when it does...I'll start dropping the lead and asking him to "stand"...then I'll walk a circle around him. If he moves to follow, I'll stick my hand up and repeat "stand" and put him back where he was. Once he's good at that, I'll widen my circle to 10' or so. You get the idea. It really doesn't take all that long before they will stand when you ask with the lead dangling. A few won't get it and for those I do something a bit different...but for most this works great and with the added benefit of them learning that whenever the saddle (or you) falls off, they are to "whoa" and "stand".