A sharp edge emerges from a dull stone, a bright fire emerges from a dark wood, a precious pearl emerges from a humble clam, and a beautiful jade emerges from an ugly raw material.

——(Jin Dynasty) Ge Hong's "Baopuzi·Outer Chapter"

The meaning of this sentence is: the sharp edge comes from the grindstone, and the bright fire comes from Burning in the dark wood, noble pearls come from humble river oysters, and beautiful gems come from ugly rough stones. This sentence is a metaphor that excellent talents must be tempered before they can grow