I undertook the first experiment on myself many, many years ago. As a boy of thirteen I left my village in the country and en-tered the second year of the Gymnasium. After several months I was admitted to the third year and then after a further six months I entered the fourth year. I remained there, working through the nights and thereby unwittingly ruining my health, at the top of the class until the eighth year of Gymnasium when I, now 18, suffered a complete collapse as my reserves of corporeal and therefore mental strength and vigour were exhausted. Due to the influence of my father, an enthusiastic apostle of science, I was now forced to realize that the threat of not being able to finish my Abitur on time, or even at all, was hanging threateningly over my head like the sword of Damocles.
I would rather have died than not have achieved my certificate, but as all attempted cures and medicines failed, there was nothing left for me to do but try to help myself. I slept for longer and longer periods, missing more and more school lessons in the process, in order to calm my excited nerves and to strengthen my ruined health. However, the longer I slept the more incapable, weaker, sicker and depressed I became. I suffered constantly from acute congestion of blood to the brain which hardly permitted the forming of a clear thought, stabbing pains in the chest, perspiring of hands and feet, and a terrible stagnation of the bowels which could not be alleviated by any of the many attempted cures.
The skin tone was yellowish and the chest narrow, otherwise my stature was normal. The doctor diagnosed catarrh of the lungs. The pulse was rapid, the nervous system excited and intellectual activity inhibited by congestion and nervous excitation. Digestion was extremely sluggish; emptying of the bowels occurred sparingly at intervals of several days. Medicines did not help. I was a pitiable, tormented creature. Meagre and temporary relief was afforded by water treatments, but the situation remained otherwise unchanged. As an example of a miserable, lamentable creature, my state was the obvious consequence of the pernicious and one-sided development of the intellect which does not know, or does not want to know, that a strong mind can only live in a strong body.* What use is it to glorify the harmonious development and the refined understanding of nature possessed by the ancient Greeks in school lessons if, in practice, one does not act in accordance with their example but rather contrary to it?
Necessity is the mother of invention; I therefore decided to shorten the overlong periods of sleep that were damaging to me. The more I followed this course, and the earlier I went to bed, the more traces of improvement were perceptible in the state of my health. But the strength necessary to meet the demands of the Gymnasium (which was by no means too "difficult" for me) was still not forthcoming.

* Although the Latin saying "mens sana in corpore sano" still holds good, one must acknowledge that the mind has often triumphed over a weak or even sickly body. Men such as Spinoza, Kant or Schiller are proof of this, as well as many unsung heroes in daily life. Note by A. Tienes.

Fortunately, the thought came to me that, as with everything in this universe, sleep must also follow strict natural laws and must thus possess the most invigorating and therefore the most healing effects. This period of sleep, of which I now began to have an idea, only needed to be discovered to be my salvation. During long periods of experiment, in an unheated room - also in winter - I brought my sleeping time further and further forward towards the hours preceding midnight. I arose, usually having awakened without out-side help at 5, 4, 3, 2:30, 1 a.m., midnight as well as at in-between times, comparing objectively and impartially the effects of the various sleeping times.
One evening, after having unsuccessfully experimented with earlier bedtimes, I went to sleep shortly before 7 p.m. (the time referred to is always local or solar time, not standard time, which must be adjusted accordingly) and slept through until 11:20pm. I woke up by myself and got up immediately - and then experienced the long-awaited and hoped-for effect which drove me on to further research with enthusiasm. All at once new life entered my tormented body: digestion started up unmistakably; the extreme nervous excitability calmed itself; the mind became clearer; courage and hope arrived. Full affinity with the universe had been conjoined, my almost superhuman struggle had been won. Even though, often hindered or disturbed by the exigencies of school, I could not always keep to the new sleeping times, my state of health improved so much owing to pre-midnight sleep that I was able to complete my Abitur on time.
As a student, in the closest rapport with nature, I rapidly became as enterprising and vigorous as I had been hesitant and weak before-hand. For the first semester of my studies, in springtime, I chose a small university city as suitable to my needs, less for the purpose of studying than to cure myself. I moved into a small, cheap and fairly quiet back room owned by a clockmaker. He was occupied with chronological time, I with natural time. Soon I was healthy enough, weather permitting, to take a regular walk at one o'clock in the morning. The night watchman of my quarter with whom I often had some conversation was surprised to find me completely sober at this late hour while the students leaving the taverns went staggering through the streets making a loud racket. Within a short time, I was known to the night watchmen and other people as a singular character. As soon as approaching dawn became noticeable I went forth, barefoot, to greet the sun. For me, every morning was a ceremonial service in the resplendent, vivid and exhilarating temple of nature under the influence of which body, soul and mind soon recovered.
When I returned home to my village after this paradisiacal summer semester, to the amazement of all those who knew me I had become a new person. I worked at home in the long holidays, which interrupted my studies regularly in late summer and springtime, on the farm run by my parents. I worked heartily in the garden, fields, byre and barn so that I became a strong and stalwart young man who was confident of his health and strength.
In these holidays the fact became apparent that in order to achieve the highest degree of physical efficiency, a sleeping period from 7 p.m. to 11:20 p.m. with rising immediately upon awakening was necessary. If I departed from these times, my efficiency and strength decreased in direct proportion to the degree of departure from this schedule. I had the same experience with regard to mental efficiency.
Later, it was no longer necessary for me to adhere to this system of natural sleep: chronic illness had been replaced with indefatigable health which withstood the hardest tests. One can understand the results of this experiment how one will: it is presented as described. It is a logical development of the experience of thousands of years.