measuring rainfalls by the standardized Cheugugi was institutionalized from May 8, 1442 (lunar calendar). From that day, the word "Cheugugi" was inscribed on the official records of the Annals of the Joseon Dynasty (조선왕조실록). The rainfall is measured by dipping a ruler and recorded by poon (Hangul: 푼, Hanja: 分) units (approximately 0.303 cm (0.120 inch)). Furthermore, the information of the time when the rain began and stopped is recorded by each case, always, throughout the nation. Examples Some Cheugudaes continue to exist: The Gwansanggam Cheugudae Daegu Sunhwadang Cheugudae (established at Daegu) Changdeokgung Palace's Cheugudae (moved to the National Palace Museum of Korea) Tongyeong Cheugudae Yeon-gyeong-dang (the royal residence in forbidden garden of Changdeokgung Palace) Cheugudae There is also Ma-jeon-gyo (Bridge) which is generally known as Supyo-gyo across the Cheonggyecheon (stream flows center of Joseon era's Seoul city (inside area of the Seoul wall), near the Gyungbok Palace). The generally known name originated from the Supyo-seok attached on the pier of the bridge. The Supyo-seok's meaning and function is "the water level gauge" of Cheonggyecheon, telling how much the stream's water level rises by rain. It was established in King Sejong the Great's reign (second year of his reign) and is existing nowadays. But 1958 when the Cheonggyecheon was covered as a road by the Korean government, it was moved to Jang-chung park and it is there. There was a plan to move the bridge to its original location, during the Cheonggyecheon restoration. But, unfortunately the plan can't be fulfilled, because there was a difference between the restored width of the Cheonggyecheon and the bridge's length. So, the bridge remains in Jang-chung Park. References Korean inventions Measuring instruments Meteorological instrumentation and equipment Rain