《论衡·卷二十二·订鬼篇》
所以得病躺在席子上，畏惧鬼会来，畏惧就呆呆的去想，呆想就会虚幻地看见鬼。
故得病寝衽，畏惧鬼至；畏惧则存想，存想则目虚见。
Therefore, sick people lying on sleeping mats are afraid of being haunted by ghosts, and they will dwell on such fears, and then have hallucinations of seeing ghosts.