I have said before that if a man wants to awaken he must hire somebody who will keep on shaking him for a long time. A man will hire somebody to wake him up but this one also falls asleep. There is also the possibility of being awakened by mechanical means. A man may be awakened by an alarm clock. But the trouble is that a man gets accustomed to the alarm clock far too quickly, he ceases to hear it.
Many alarm clocks are necessary and always new ones.
Otherwise a man must surround himself with alarm clocks which will prevent him sleeping. But here again there are certain difficulties. Alarm clocks must be wound up. In order to wind them up one must remember about them. In order to remember about them one must wake up often.