Liu Gongquan was a calligrapher in the Tang Dynasty who was well-behaved and knowledgeable. He was especially good at writing calligraphy, so the emperor valued him very much. He asked him to be the teacher of the prince. Once Emperor Mu Zong of the Tang Dynasty summoned Liu Gongquan and asked him how he could write well. Liu Gongquan replied: "A correct heart means a correct pen. It can be the law.”