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