Beautiful! I imagined it twice. Firstly before I understood the reference and was sitting by a fire inside a cave that could be any cave watching the horse gallop by outside and secondly when the wall paintings came to life. I enjoyed it both times but my reading of it was so enriched once I understood the reference. Thank you.
Engaged is the mind in thoughts of own
Absorbed is the mind in thoughts of own
A disturbance breaks peace of mind
Everything else going on in mind prior is now put on hold.
Exactly what draws the mind's attention is the horse and that is what makes the entire description of a horse galloping absolutely interesting.