釋門歸敬儀 2.19

2.19

二、明稽首者。古文為稽，今則為稽。俗所常行，不必從古。《白虎通》云：「稽者，至也。首者，頭也。」言下拜於前，頭至地。即《說文》云：「謂下首者為稽也。」《三蒼》云：「稽首，頓首也。」謂以頭頓於地也。然今行事頓首為輕，謂長立頓首於空也。故晉時釋慧遠與俗士書，但云「頓首」而不揖也，謂非是曲身而但立也。故長揖司空，不必身曲。然頓首、頓顙，俗中恒度，首頭之總名，顙額之別目。然古儀有「稽首稽首」、「頓顙頓顙」，上敬天子殷重之謂，故重言之。準此頓顙，以額至地而拜也。

Second, explaining bowing the head to the ground (jisou): In ancient script it was written 稽 (ji), but now it is written 稽. It is commonly practiced in secular custom and does not necessarily follow the ancient form. The Baihu Tong says: "Ji means to reach; sou means the head." It means bowing down in front with the head reaching the ground. The Shuowen Jiezi says: "Lowering the head is called ji." The Sancang says: "Bowing the head to the ground is kowtowing (dunsou)"; that is, placing the head down to the ground. However, in current practice, kowtow is lighter, meaning standing tall and nodding the head in empty air. Therefore, when Shi Huiyuan of the Jin wrote letters to secular gentlemen, he only wrote "kowtow" and did not make a cupped-hand bow (yi), meaning he did not bend his body but merely stood. Thus, making a deep cupped-hand bow to the Minister of Works does not necessarily require bending the body. However, kowtow (dunsou) and pressing the forehead (dunsang) are standard practices in secular custom; sou is the general name for the head, and sang is the specific name for the forehead. In ancient rites, there were "bowing the head to the ground, bowing the head to the ground" and "pressing the forehead, pressing the forehead," which expressed profound solemnity in venerating the Son of Heaven, hence repeated twice. According to this, pressing the forehead is bowing with the forehead touching the ground.