Zheng Xuan
"Gu" meaning 2.3 "ghost of a person whose severed head was impaled on a stake" refers to the severe Han Dynasty "dismemberment (as tortuous capital punishment)" for criminals convicted of practicing "gu"-sorcery (see 2.6). Groot "Plate VI, Punishment of Cutting Asunder" provides a gruesome illustration. The "Zhouli" commentary of Zheng Xuan (cf. 2.2) notes, "Those who dare to poison people with "ku" or teach others to do it will be publicly executed".