"To sleep, perchance to dream"
-Hamlet

"Methought I heard a voice cry 'Sleep no more! Macbeth does murder sleep', the innocent sleep, Sleep that knits up the ravell'd sleeve of care, The death of each day's life, sore labour's bath, Balm of hurt minds, great nature's second course, Chief nourisher in life's feast,--" "Still it cried, 'Sleep no more!' to all the house, 'Glamis hath murder'd sleep, and therefore Cawdor Shall sleep no more; Macbeth shall sleep no more.' "
-Macbeth, Act 2, Scene 2

"A great perturbation in nature, to receive at once the benefit of sleep, and do the effects of watching!"
-Macbeth, Act 5, Scene 1

"O sleep, O gentle sleep, Nature's soft nurse, how have I frighted thee, That thou no more wilt weigh my eyelids down And steep my senses in forgetfulness?"
-King Henry I, Act 3, Scene 1

William Wordsworth had trouble sleeping as well:

"To Sleep"
"A flock of sheep that leisurely pass by One after one; the sound of rain, and bees Murmuring; the fall of rivers, winds and seas, Smooth fields, white sheets of water, and pure sky- I've thought of all by turns, and still I lie Sleepless; and soon the small birds' melodies Must hear, first utter'd from my orchard trees, And the first cuckoo's melancholy cry. Even thus last night, and two nights more I lay, And could not win thee, sleep , by any stealth: So do not let me wear to-night away. Without thee what is all the morning's wealth? Come, blessed barrier between day and day, Dear mother of fresh thoughts and joyous health!"