釋氏要覽 3.116

3.116

木版為之。形量似笏。中作孔。施細串於耳下。頭戴去額四指。坐禪人。若昏睡頭傾則墮以自警。

Made of a wooden board, its shape and size resemble a court tablet. A hole is made in the center, and a thin cord is attached beneath the ear; worn on the head four finger-widths from the forehead. When a meditator nods off in drowsiness and the head tilts, it falls off to alert them.