悬梁刺骨

Explanation: Described as hard to learn. 　　Source: "Warring Qin policy a" (Su) reading drowsiness, cited cone from the thorns of its shares. "" Tai Ping Yu Lan "Volume three hundred sixty-three cited" Han "characters SUN Jing Wen Po, studious, Chen Xi endlessly, until exhausted sleep sleep sleep, tied to the first, when the world is hanging beams ◇ Daru." Thesaurus:  Curiousness tireless, Cigu hang oneself from a beam, Night time candlelight, Daytime tillage night to chant