《史记·七十列传·大宛列传》
如今出使大夏，要是从羌人居住区经过，则地势险要，羌人厌恶；要是稍微向北走，就会被匈奴俘获。从蜀地前往，应是直道、又没有侵扰者 。
今使大夏，从羌中，险，羌人恶之；少北，则为匈奴所得；从蜀宜径，又无寇。 
Today when sending envoys to Da Xia, if they pass through the region inhabited by the Qiang, the terrain will be difficult and the Qiang will resent it; if they go slightly north, they will be taken prisoner by the Xiongnu. The route from Shu should be a straight path, and there will be no harrassment.