《淮南子·天文训》
而到了悲泉，全天行程将完，于是让御手卸车息马，悬车休息。
至于悲泉，爱止其女，爱息其马，是谓县车。
<translation>Upon the arrival at the Bei Springs, the entire day’s itinerary was completed. Then the imperial charioteer unhitched the chariot and rested the horse, and hung the chariot for a break. 