The Western world did not find out how to measure humidity using a ball of wool and a piece of rock until the year 1450, about 1,000 years after the Chinese invented their system The wind cone is a device in vented by Chang Heng of the Eastern Han dynasty.
西方一直到西元一四五○年，才知道利用這種原理，而以羊毛球和石塊做成濕度計，比中國晚了一千餘年。兒童博物館中的這座濕度計是由劉昭明教授所考證設計的。