what this sentence refer to? " nor may young men behold it until they have been beaten with rods"

This is from Herod's famous monologue. He claims to have many priceless jewels including a crystal,

"I have a crystal, into which it is not lawful for a woman to look, nor may young men behold it until they have been beaten with rods. "

Apparently this crystal is so enchanted and forbidden that only a man that has been punished, forced to endure some sort of penance, can look upon it. Being beaten with rods was a Roman form of punishment. The context of this is Herod asking Salome what he can desire more than these priceless things being offered.