Makatura Dead Upright in the Saddle

From E6.33, Makatura Falls to Bahram Chubin. It illustrates E6.33.18–23:

E6.33.18
He chose a shaft to pierce the armor through;Before it, stone and iron softened too.
E6.33.19
Through spine and mail the bodkin arrow sped,And pinned him to the saddle-tree stone-dead;
E6.33.20
For he had lashed his feet before the fight,Vowing never to turn his horse in flight:
E6.33.21
Now lifeless on the mane his head was thrown,Upright in death, as motionless as stone!
E6.33.22
Then Bahram told the Khan, “The chief lies dead;He needs a gravedigger to make his bed.”
E6.33.23
The Khan replied, “Look closer; there he liesAlive, asleep before our very eyes.”