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During the Middle Ages,

a specific monk was assigned the duty of checking with a lantern if any of the monks was sleeping during Matins and waking him up.

“Staying awake during the lengthy readings of Nocturns was evidently a problem. The Cluny customary provides for a lantern-bearer to perambulate the choir to make sure that everybody is awake. If he comes upon a monk who has fallen asleep during the lessons, he does not speak, but gently moves the lantern to and fro close to his face until he wakes.” -
Medieval Monasticism, C.H. Lawrence, Second Edition, 1990, p. 113
Ultraviolet
Umberto Eco elaborates in describing the practice, stating the monk who'd caught sleeping had to take up the lantern instead and check for other sleepers