Wu Shen Ji You Da Yi Tu (戊申己酉大驿土) refers to the earth element associated with Wu Shen (戊申) and Ji You (己酉). Shen (申) corresponds to Kun (坤), which represents the earth, and You (酉) corresponds to Dui (兑), which represents the marsh. The earth of Wu (戊) and Ji (己) is placed above the Kun marsh, distinguishing it from other superficial types of earth. Therefore, it is called Da Yi Tu (大驿土), the Great Post Earth.