Strongly associated with Jin Yong's
笑傲江湖 (Xiào Ào Jiānghú, The Smiling, Proud Wanderer): the
葵花宝典 (Kuíhuā Bǎodiǎn, 'Sunflower Manual') famously opens with the line
欲练神功,
必先自宫 ('to master this divine skill, first castrate yourself'). The phrase is now a meme for absurd, painful prerequisites.