Generally speaking, that which makes man man is the meaning of his ceremonial usages. The first indications of that meaning appear in the correct arrangement of the bodily carriage, the harmonious adjustment of the countenance, and in the natural ordering of the speech. When the bodily carriage is well arranged, the countenance harmoniously adjusted, and speech naturally ordered, the meaning of the ceremonial usages becomes complete, and serves to render correct the relation between ruler and subject, to give expression to the affection between father and son, and to establish harmony between seniors and juniors. When the relation between ruler and subject is made correct, affection secured between father and son, and harmony shown between seniors and juniors, then the meaning of those usages is established. Hence after the capping has taken place, provision is made for every other article of dress. With the complete provision of the dress, the bodily carriage becomes (fully) correct, the harmonious expression of the countenance is made perfect, and the speech is all conformed to its purposes. Hence it is said that in capping we have the first indications of (the meaning of the) ceremonial usages. It was on this account that the sage kings of antiquity made so much as they did of the capping.
Anciently, when about to proceed to the ceremony of capping, they divined for the day by the stalks, and also for the guests (who should be present). In this way did they manifest the value which they attached to capping. Attaching such a value to it, they made the ceremony very important. They made the ceremony so important, showing how they considered it to lie at the foundation of the state's (prosperity). Hence (also) the capping took place at the top of the eastern steps, (appropriate to the use of the Master) - to show that the son would (in due time) take his place. (The father) handed him a (special) cup in the guests' place. Three caps were used in the ceremony, each successive one more honourable, and giving the more importance to his coming of age. When the capping was over, he received the name of his maturity. So was it shown that he was now a full-grown man. He presented himself before his mother, and his mother bowed to him; he did the same before his brothers and cousins, and they bowed to him - he was a man grown, and so they exchanged courtesies with him. In the dark-coloured cap, and the dark-coloured square-cut robes, he put down his gift of introduction before the ruler, and then proceeded with the proper gifts to present himself to the high ministers and Great officers, and to the old gentlemen of the country - appearing before them as a man grown.
Treating him (now) as a grown-up man, they would require from him all the observances of a full-grown man. Doing so, they would require from him the performance of all the duties of a son, a younger brother, a subject, and a junior. But when these four duties or services were required from him, was it not right that the ceremony by which he was placed in such a position should be considered important?
Thus when the discharge of filial and fraternal duties, of loyal service, and of deferential submission was established, he could indeed be regarded as a (full-grown) man. When he could be regarded as such, he could be employed to govern other men. It was on this account that the sage kings attached such an importance to the ceremony, and therefore it was said, that in capping we have the introduction to all the ceremonial usages, and that it is the most important of the festive services.
Source: Chinese Text Project http://ctext.org/liji. English translation "Sacred Books of the East, volume 28, part 4: The Li Ki", James Legge, 1885