horse with flexible legs will necessarily be able to rear his body.
What we want is a horse with supple loins, and not supple only but
short and strong (I do not mean the loins towards the tail, but by the
belly the region between the ribs and thighs). That is the horse who
will be able to plant his hind-legs well under the forearm. If while
he is so planting his hind-quarters, he is pulled up with the bit, he
lowers his hind-legs on his hocks[2] and raises the forepart of his
body, so that any one in front of him will see the whole length of his
belly to the sheath.[3] At the moment the horse does this, the rider
should give him the rein, so that he may display the noblest feats
which a horse can perform of his own free will, to the satisfaction of
the spectators.

[1] {lampros}. Cf. Isae. xi. 41 ("On the estate of Hagnias"), Lys.
xix. 63 ("de Bon. Arist.").

[2] See Berenger, ii. 68.

[3] Lit. "testicles."

There are, indeed, other methods of teaching these arts.[4] Some do so
by touching the horse with a switch under the hocks, others employ an
attendant to run alongside and strike the horse with a stick under the
gaskins. For ourselves, however, far the best method of
instruction,[5] as we keep repeating, is to let the horse feel that
whatever he does in obedience to the rider's wishes will be followed
by some rest and relaxation.

[4] Lit. "People, it must be admitted, claim to teach these arts in
varous ways--some by . . . others by bidding . . ."