Literature Reference: 刺股情方励，偷光思益深。—— 《惜分阴》 Stabbing the thigh to stay awake, and stealing light to deepen thought. Source from 'Xi Fen Yin'.
刺: To pierce, to stab with something sharp.
股: Thigh.
Meaning: Stabbing the thigh symbolizes diligence and perseverance in study.