Liu Kun, a poet in the Jin Dynasty, wrote a poem praising soft sword in Poems for Lu Zhan: "What does it mean to make steel?" There are also traces of soft sword in Shen Kuo's Meng Qian Bi Tan in Song Dynasty. He said, "Bend as hard as a hook and it will be as loud and straight as a string", "You can bend it in a box and straighten it vertically".