"In an ideal condition, children should be brought up in the country as much as possible. An abundance of simple well-cooked food in sufficient variety, ample time at table, where an atmosphere of light gaiety should be cultivated, and a period free from restraint, both before and after meals, should be considered fundamental essentials.
"The exercise of the body must be attended to in the shape of games.
"But severe exercise should only be allowed under adequate medical control, and should be increased very gradually. In the case of girls, let them run, leap and climb with their brothers for the first 12 years or so of life. But as puberty approaches, with all the change, stress and strain dependent thereon, their lives may need appropriate modification. Rest may be necessary during the menstrual periods of early years, and, perhaps, milder more graduted exercise should be taken at other times. In the same way, all mental strain should be diminished. Instead of pressure being put on a girl's intellectual education at about this time, as is too often the case, the time devoted to schools and books should be diminished. Education should be on broader, more fundamental lines, and much time should be passed in the open air. With regard to the mental training of both sexes two points must be borne in mind. First, that an ample number of hours should be set on one side for sleep, up to ten years of age not less than 11, and up to 20 years not less than nine. Secondly, that the time devoted to 'bookwork' should be broken up into a number of short periods, very carefully graduated to the individual child.
"In every case where there is a family tendency towards any certain disease or weakness, that tendency must determine the whole circumstances of the child's life. That diathesis which is most serious and least regarded, the nervous excitable one, is by far the most important and the most difficult to deal with. Every effort should be made to avoid the conditions in which the heredity predisposition would be aroused into mischievous action, and to encourage development on simple unexciting lines. The child should be confined to the schoolroom but little, and receive most of his training in wood and field. Other diathesis (the tuberculous, rheumatic, etc.) must be dealt with in appropriate ways.
"The adolescent is prone to special weakness and moral perversions. The emotions are unstable, and any stress put upon them may lead to undesirable results. Warm climate, tight-fitting clothes, corsets, rich foods, soft mattresses or indulgences of any kind, and also mental over-stimulation, are especially to be guarded against. The day should be filled with interests of an objective (in contradistinction of subjective) kind, and the child should retire to bed at night healthily fatigued in mind and body. Let there be confidence between mother and daughter, father and son, and, as the years bring the bodily changes, those in whom the children trust can choose the fitting moments for explaining their meaning and effect, and warning against abuses of the natural functions."
--Encyclopedia Britannica, 14th Edition, (c) 1929-1938, author not listed.
(The article might have been published also for an earlier edition, given the admonition against corsets.)
"Healthly fatigued," as in work the little buggars 'til they drop. And, anybody who sleeps on a soft mattress in a warm climate ... Well, you're doomed.