I tried to search for similar threads, but I couldn't find any! So here goes.
For this you need a Magic Broom and The Horseman's Reins.
It's rather simple, and I am not sure wether it's an exploit or not .. but I noticed that you could mount your Magic Broom while flying on your Horseman Reins or reverse!
1. You mount your Magic Broom or The Horseman's Reins.
2. You fly a good distance up the air.
3. Mount the mount you did not use.
If you don't fly high enough into the air, you will most likely fall down and die ... like the first couple of times I did it. Luckily we mages don't have too high repair bills!
I'll try fix a youtube video too!
Edit: Meh, didn't notice the error in the title of my topic.
Edit: Youtube video uploaded!