천자문
Some "Sangpyeong Tongbo" cash coins contained characters from the Thousand Character Classic ("Ch'ŏnjamun") to determine by which furnace they were cast, the Thousand Character Classic was used in the far east for teaching Chinese characters and was a large poem which consisted of 250 phrases with each one of these phrases being only composed 4 Hanja characters. The entire Thousand Character Classic is composed of 1000 Chinese characters and no point is a single character repeated.