On the Cavalry Commander (6.2-6.3)

But if he faces in the opposite direction to the horse and sits by the shoulder out of reach of his leg when he cleans him, and rubs him down so, then he will come to no harm, and can also attend to the horse’s frog by lifting up the hoof.[*] Let him do exactly the same in cleaning the hind-legs.

The man employed about the horse is to know that in these operations and in all that he has to do he must be very chary of approaching from the head or tail to do his work. For if the horse attempts to show mischief he has the man in his power in both these directions; but if he approaches from the side he can manage the horse with least danger to himself and in the best manner.