The following is from a talk by the Mother, dated 10 March 1951 ( complete talk here). Here she makes some very interesting comments regarding the "mental fortress", the idea that we create a subjective mental image of Reality, which we mistake for Reality itself.
There are people who spend their life organising their mind. I have known some who had made of their mind a kind of fortress, a huge construction (I am speaking of people who had uncommon mental capacities). They had made of their mind quite a big edifice, very powerful and of such a fixity, with such solid walls that they had lost all contact with the outer mental world: they lived completely within their own construction and all the phenomena of their consciousness were of their own making - they had no longer any contact with the outside mental world. They retained contact with their own vital and their body, in a way, but all the phenomena of their consciousness were lodged within their mental construction - they could no longer get out of it. Well, this happens very strongly to people who seek for a spiritual life through the classical methods of a renunciation of the material consciousness, a concentration on their inner being and identification with it. If I gave you the names of some, you would be quite astonished. They construct for themselves a conception in which one finds all the gradations of the mind, a construction so solid and so fixed that they become imprisoned within it and when they believe they have reached the supreme Truth, they have only reached the centre of their own mental construction.
And they have all the experiences they used to foresee: the experience of liberation, the experience of going out of the body, the experience of identification with the Supreme, all, all, but all of their own making; this has no contact with the universal reality. Then if someone touches it, if for some reason or other someone has the power to touch it or simply to make a breach in one of the walls, at first they are completely upset, then they come to regard the force that could do this as a force of terrible destruction, a manifestation of a hostile force of the worst kind !
Some personal comments and interpretation:
I find the above provides an interesting interpretation of the mental and claimed spiritual ("nirvikalpa samadhi") teachings of Ken Wilber, especially in view of his recent behaviour. See also the comments in my essay on Integral World
My earlier esoteric understandings also had something of the "mental fortress" about them (albeit not to such an extreme degree), but I since came to realise the importance of going beyond the mental bubble and harmonising with the Psychic Being.