Although it is possible to do just about anything magically or mechanically, very little is purely one or the other. Many times magic can serve as a hedge to augment a technology.

For example, many found that magically rewinding a mainspring was easier than using a team of horses. It was more expensive, but several magnitudes of time faster.

Magic has also been used to create to solve problems with aether flyers. Although mechanically possible to seal a ship against the vacuum of outer space, it was usually easier to have a mage cast a spell to do so. (The also has the side benefit of making an aether flyer look like it is carved out of a single block of wood.) If a ship did not need to travel through a reagent vacuum, no one would notice. Magic is also used to create artificial gravity, and even as a means of propulsion.

The mainspring was the first great mechanical invention. Romans sought to improve upon the mechanism the Greeks used in a water clock. In other words, the goal was to produce a clock that did not need large amounts of water. Leave it to an emperor to require a device intended as nothing more as spectacle that ended up changing the world.

Mainsprings have to be wound, but refinements since the ancient design have made them relatively inexpensive to create. Magic may be simpler, but it is often more expensive.

In addition to timepieces, mainsprings have served as power sources for a variety of things from weapons to automatons to aether flyers and more.

I'm one of those world builders that begins with core ideas from which to create many possibilities. Frankly, it can give me a wicked headache sometimes.

For the sake of simplicity, we'll call this universe Maderia. (It's a Spanish dessert wine.)

In Maderia, the following facts define the universe:

Sound requires a medium to travel through. It is usually air, but like our universe, it can be anything. Also, the denser the medium, the faster sound travels through that medium.

Light also requires a medium to travel through. It is the luminiferous aether. The aether has a constant velocity (thus no color shifting of stars in the sky) except where aether rivers exist.