540. 'And upon his heads seven diadems' signifies all the truths of the Word falsified and profaned. By the 'diadems' or precious stones are signified the truths of the Word, specifically the truths of the sense of the letter of the Word, but here those truths falsified and profaned, because they were seen upon the seven heads of the dragon, by which is signified insanity resulting from truth falsified and profaned (n. 538).  That by 'diadems' or precious stones the truths of the sense of the letter of the Word are signified may be seen in THE DOCTRINE OF THE NEW JERUSALEM CONCERNING THE SACRED SCRIPTURE (n. 43-45), where it has been shown that Divine Truths in ultimates, which are the truths of the sense of the letter of the Word, are signified:-
By the twelve precious stones in Aaron's breastplate, which was the Urim and Thummim Exod. xxvii 6, 15-21. 30.
By the precious stones in the garden of Eden, in which the king of Tyre is said to have been Ezek. xxxiii 12, 13.
Also by the twelve precious stones out of which the foundations of the wall of the New Jerusalem were [formed] Rev. xxi 17-20.
The reason why the truths of the sense of the letter of the Word are signified by the 'diadems' or precious stones is because all things of the sense of the letter of the Word are transparent before the angels by virtue of its spiritual sense, thus of the light of heaven in which the spiritual truths of the Word are. For a 'stone' in the Word signifies a truths its ultimates, consequently a 'precious stone' signifies that truth transparent.  The reason why falsified and profaned truths of the Word are also termed 'diadems' is because they shine of themselves with whomsoever they may be, just like diadems on earth in whosesoever hand they are. At one the it was given me to see adulterous women, as they came first into the world of spirits from earth, adorned with diadems, and also Jews selling diadems which they had procured to themselves out of heaven. From this it was plain that the evils and untruths with such do not change the light and splendour of the truths of the Word. Similar things are therefore also signified by:-
The ten diadems upon the horns of the beast coming up out of the sea Rev. xiii 1.
And by the precious stones upon the woman sitting upon the scarlet beast Rev. xxii 3-5.
That the truths of the Word are the things signified by diadems is quite plain in the Apocalypse:-
Many diadems were seen upon the head of the One sitting upon the white horse, Whose Name was the Word of God Rev. xix 12, 13.