"That's Once!" joke

After a whirl wind courtship and marriage, the happy couple climb into the carriage
(amid rice sprinkling on them) and the horse trots off taking them to their farm home from the
church.
The horse carried then up and down the foothills towards their homestead. On a
particularly steep hill, the horse stumbled and caused the couple to be uncomfortably jolted in their
seats.
The farmer calmly stopped the horse. Got off the wagon, walked up to the horse,
grabbed it by the harness, looked it in the eyes, and said in a loud voice "that's once".
The farmer got back in the wagon and the horse plodded off. Again they were going
over a particularly difficult portion of the road and the horse stumbled and jolted the couple in the
wagon.
The farmer again got out of the wagon, walked up to the horse, stared it in the eye,
and said "that's
twice". The new wife was perplexed by all this but did not even know how to begin to
ask what he was
doing. They traveled further down the road, and the horse stumbled a third time,
jolting the couple.
The farmer got out of the wagon, went to the back of the wagon, took his gun, and
promptly shot the
horse in the head, leaving it lying in the middle of the road. Dead.
The new wife gaped in astonishment at her husband. she said, "What the hell did you
do that for,
horses are very expensive, and how the hell do you expect me to get to the farm now?
I cannot believe
you did that!"
The farmer walked up to the wife, looked her in the eye and said, "that's once".