The Taipei Palace Museum has been condemned for loaning a centuries-old calligraphy masterpiece - considered one of China's most precious ancient treasures - to Japan. "Draft of a Requiem to My Nephew" was written by Yan Zhenqing in the year of 758, to immortalize his nephew Yan Jiming, and his cousin Yan Gaoqing, who died in a Tang Dynasty (618-907) civil war.