The exact definition of this range varies. An old source uses Kunlun to mean the mountain belt that runs across the center of China, that is, Kunlun in the narrow sense: Altyn Tagh along with the Qilian and Qin Mountains. A recent source has the Kunlun range forming most of the south side of the Tarim Basin and then continuing east south of the Altyn Tagh. Sima Qian ("Records of the Grand Historian", scroll 123) says that Emperor Wu of Han sent men to find the source of the Yellow River and gave the name Kunlun to the mountains at its source. The name seems to have originated as a semi-mythical location in the classical Chinese text "Classic of Mountains and Seas".