"Mastery is achieved when the mind can concentrate on any object from the smallest atom to the entire cosmos." Sutra 1.40 Maehle translation
The two translations of the Yoga Sutras that I use the most were done by Iyengar and Maehle. It's interesting to me that the commentary in both translations of this sutra is similar. They both talk about starting to learn to pay attention by using more accessible "objects of meditation" and working up to more challenging ones. It seems to me like a parallel to challenging the breath through asana practice. You start the practice with fundamental asanas. When the breath is steady and easy, you add more challenging asanas, pushing the edges of maintaining a steady breath. It makes sense to me that steadying the mind would work the same way. Start with the basics, then, when the mind is steady, add more challenge.
Ultimately, I suppose the two are really not that separate. Pranayama is, after all, using breath control to control energy and mind. Breath is both an object of meditation and a physical reflection of the steadiness or unsteadiness of the mind.
...I do have the feeling though, when it comes to a steady mind, I'll be working on the basics for a long time...