Rome was the cultural epicenter of the ancient world. It was renowned for its law and order, piety, engineering, and fine art. But it was still a terribly brutal civilization by modern standards.
In the mid-5th century BC, Rome established its first legal code, the Twelve Tables. Oddly, the code was silent on the subject of murder. As a result, unwritten codes of retribution were created to deal with homicide.
Parricide, the act of killing one’s own parent, was known to result in a particularly gruesome punishment. Via Tacitus:
The traditional punishment for parricide…is as follows: the condemned person is beaten with blood-colored sticks, then sewn in a sack with a dog, a rooster, a viper, and a monkey, and thrown into the deep sea, if the sea is nearby; otherwise, in accordance with the law passed by the deified Hadrian, he is thrown to wild beasts. (Justinian’s Digest 48.9.9)
If you’re wondering if this method of execution was ever enforced, the answer is yes. Livy tells us that one Publicius Malleus was sewn in a sack and tossed in the sea for killing his mother. (It’s unclear if any animals accompanied Malleus on his voyage.)
It’s worth noting that the Founding Fathers, who were highly educated in classical history, were probably aware of this gruesome practice.
In fact, it's quite possible that executions such as that endured by Malleus were what the Framers were referring to in the Eight Amendment, which banned “cruel and unusual punishments.”