정철
Song Ikpil (February 10, 1534 - August 8, 1599) was a politician and Neo-Confucian scholar and educator. His pennames were Gubong (구봉, 龜峰) and Hyeonseung (현승, 玄繩), and his courtesy name was Unjang (운장, 雲長). Song was best friends of Yi I, Seong Hon and Jeong Cheol and taught Kim Jang-saeng.