Wikipedia spelunking
I wrote a script to grab five random wikipedia articles every day. Sometimes it pays off with something interesting I'd probably never have read about. Like this one about Korean rain gauges:
Ch'ŭgugi... were rain gauges invented and used during the Joseon dynasty of Korea. They were invented and supplied to each provincial office during the reign of King Sejong the Great.
Early in the Joseon dynasty, a system was introduced to measure and report regional rainfall for the sake of agriculture. However, the method to measure rainfall in those days was primitive, recording the depth of rain water in puddles.
This method could not tell the exact rainfall, because rainwater is absorbed differently into the ground according to the local soil. To prevent errors of this kind, King Sejong the Great ordered the Gwansanggam... to build a rainwater container, the ch'ŭgugi, made of iron in August 1441.