《黄帝内经·灵枢·禁服》
寸口脉比人迎脉盛大四倍，称为阴气被阳气关闭在内，内关的脉象在盛大的同时而且疾速，属于死证而不能救治。
寸口四倍者，名曰内关，内关者，且大且数，死不治。
If the Cun Kou pulse is four times stronger than the Ren Ying pulse, it means that the yin qi is closed off by the yang qi. The pulse in the Nei Guan is strong and fast at the same time, and it is a fatal symptom that cannot be treated.