in the text known as the "xin lun" written by huan tan about 20 ad (during the usurpation of wang mang), it states that the legendary mythological king known as fu xi was the one responsible for the pestle and mortar, which evolved into the tilt-hammer and then trip hammer device (see trip hammer). although the author speaks of the mythological fu xi, a passage of his writing gives hint that the waterwheel was in widespread use by the 1st century ad in china.