Although the Chinese government has stated that rainfall measurements were recorded as early as 3,000 years ago during the Chou dynasty, the first instrument designed specifically to collect and measure rainfall was invented by King Sejong's son, the future King Munjong, in Korea during in the 1400s. King Sejong wished to improve the technology used in Korean agriculture, and some of the most accurately maintained rainfall records were recorded during this time. The newly invented rain gauge, called a cheugugi, was sent to provincial Korean villages to measure rainfall as an indicator of farmers' potential harvest yields and served as a basis of determining local taxation rates.
Prior to the invention of the cheugugi, the rainfall in King Sejong's realm was measured by determining the depth of rain water in puddles. This primitive method, however, did not provide accurate readings because of the differences in absorption rates among varying soil types. To correct these errors, King Sejong charged the kingdom's research institute, the Gwansanggam, with the task of creating a device capable of taking accurate readings and to develop a standardized measurement system. After the cheugugi and the measurement system were created, the king ordered his appointed provincial governors to install the device in each of their office courtyards. They were also ordered to remain personally responsible for measuring and recording the rainfall readings.
The first cheugugis were made from iron, but later versions were constructed from either ceramic or copper. The device is cylindrical in shape and is supported by a hexahedral stone base. The reasonable height of the cheugugi assures that additional splashed water can't flow into it.