Jeremy Taylor thought that for a healthy adult, three hours in twenty-four were enough for all the purposes of sleep. Baxter thought four hours about a reasonable time; Wesley, six; Lord Coke and Sir Wm. Jones, seven; and Sir John Sinclair, eight. These were the theories of men who were all eminent for their learning, and most of them for their piety. How far their practice corresponded with their theories, we are not, in every instance, told.
But to come to the practice of several persons who have been distinguished in the world. General Elliot, one of the most vigorous men of his age, though living for his whole life on nothing but vegetables and water, and who at sixty-four had scarcely begun to feel the infirmities of old age, slept but four hours in twenty-four. Frederick the Great of Prussia, and the illustrious British surgeon, John Hunter, slept but five hours a day. Napoleon Bonaparte, for a great part of his life, slept only four hours; and Lord Brougham is said to require no more. Others, in numerous instances, require but six hours. But there are others still, who consume eight.
The conclusion—in my own mind—is, that with a good constitution and active habits, men may habituate themselves to very different quantities of sleep. Still I think that six hours are little enough for most persons; and if a child, on arriving at maturity, is not inclined to sleep much longer than that, I should not regard him as wasting time. Most persons, it appears to me, require six hours of sound sleep in twenty-four;—I mean between the ages of twenty and seventy.
Macnish is the most liberal modern writer I am acquainted with, in his allowance of time for sleep. Speaking of the wants of adults he says—“No person who passes only eight hours in bed can be said to waste his time in sleep.” Yet he obviously contradicts himself on the very same page; for he says expressly, that when a person is young, strong and healthy, an hour or two less may be sufficient. But an hour or two less than eight hours reduces the amount to seven or six hours. And taking the whole period of life, to which he probably refers—say from eighteen to forty—into consideration, there is a very considerable difference between six hours and eight hours a day. If six hours are “sufficient,” it cannot be right to sleep eight hours.
Let us here make a few estimates. If six hours are sufficient for sleep between the ages of eighteen and forty, he who sleeps eight hours a day, actually loses 16,060 hours—equal to nearly two whole years of life, or about two years and three quarters of time in which we are usually awake. This, in the meridian of life, is not a small waste. Permit it to every person now in the United States, and the sum total of wasted time to a single generation, would be 25,649,098 years—equal to the average duration of the lives of 854,970 persons. The value of this time, as a commodity in the market, at a low estimate—only forty dollars a year—would be over A THOUSAND MILLIONS of DOLLARS! And its value, for the purposes of mental and moral improvement, cannot be estimated except in ETERNITY!