The story comes from Sima Qian's biography of Laozi in the Records of the Grand Historian, written around 100 BCE, and Sima Qian himself is notably uncertain about whether Laozi existed and offers several competing accounts in the same passage. In the version that stuck, Laozi was an archivist at the Zhou court who, seeing the dynasty decay, left. At the western pass the gatekeeper Yin Xi recognised him and refused to let him through until he set his teaching down, whereupon he wrote something over five thousand characters in two parts, on the Way and its power, and departed — and, Sima Qian ends, no one knows what became of him. It is the founding text's origin story and it is an account of reluctance: the book exists because a border official would not open a gate. Later tradition extended the journey westward, and the polemical Huahujing claimed he continued to India and became the Buddha.