Wide water depth means profound knowledge. From Tang Hanyu's "The Wall of the Pavilion in Lantian County": "Cui, Bo Ling, and Zhi made academic achievements to preserve what they have and show their enthusiasm.
"
Ji hongcheng
The water is deep. From Lv Kun's Preface to My Love in the Ming Dynasty: "Is it both free and generous? Hey, a thousand miles flows, and you can reach four without being poor.