From
韩愈's
符读书城南, written to urge his son
符 to study. Two boys alike as children grow apart, and by thirty one is a dragon and the other a pig. The one who studied is
飞黄, a legendary divine horse, galloping off too fast to look back at the toad,
蟾蜍. The line gave the idiom
飞黄腾达 'to rise fast in the world'.
