Which president needed 11 hours of sleep each night?

The 30th President of the United States Calvin Coolidge went to bed at 10, got up between 7 and 9, and always took an afternoon nap lasting 2 to 4 hours which resulted in an average of 11 hours sleep per day/night. It was rummered that this overwhelming need for sleep was caused by the grief and depression over the loss of his 16 year old son to sepsis. It is also said that he always had a glass of buttermilk before retiring to bed to settle his stomach which could also indicate he was under a great deal of emotional distress.