“The essential meaning of the crown is derived from that of the head, with which it is linked—unlike the hat—not in a utilitarian but in a strictly emblematic manner. By reference to level-symbolism, we may conclude that the crown does not merely surmount the top of the body (and of the human being as a whole), but rises above it and therefore symbolizes, in the broadest and deepest sense, the very idea of pre-eminence. That is why a superlatively successful achievement is spoken of as a ‘crowning achievement’. Hence the crown is the visible sign of success, of ‘crowning’, whose significance reaches beyond the act to the person who performed it.
The metal crown, the diadem and the crown of rays of light, are symbols of light and of spiritual enlightenment. In some books of alchemy there are illustrations showing the planetary spirits receiving their crown—that is, their light—from the hands of their king—that is, the sun. The light they received from him is not equal in intensity but graded, as it were, in hierarchies, corresponding to the grades of nobility ranging from the king down to the baron. Books on alchemy also stress the affirmative and sublimating sense of the crown. In Margarita pretiosa, the six base metals are first shown as slaves, with their uncovered heads bowed low towards the feet of the ‘king’ (that is, gold); but, after their transmutation, they are depicted wearing crowns on their heads. This ‘transmutation’ is a symbol of spiritual evolution whose decisive characteristic is the victory of the higher principle over the base principle of the instincts. That is why Jung concludes that the radiant crown is the symbol par excellence of reaching the highest goal of evolution: for he who conquers himself wins the crown of eternal life.”
Source: J.E. Cirlot, A Dictionary of Symbols, p. 72