When his ability to practise ultramystic meditation becomes well-developed, the student may frequently find himself suddenly waking up during the night at an hour earlier than that to which he is accustomed. His mind will be alert and attentive and he will not be able to fall asleep again. This is a signal to him to begin his meditation practice. If he heeds this mysterious and silent injunction, the ultimate inward effectiveness and ultimate outward results of such meditation will be far above the ordinary.
-- Notebooks Category 23: Advanced Contemplation > Chapter 6: Advanced Meditation > # 76