This is actually quite a common theme in Buddhist literature. Apart from the central concept of the nature of mind that is by definition unthinkable (in the sam

This is actually quite a common theme in Buddhist literature. Apart from the central concept of the nature of mind that is by definition unthinkable (in the same way that the eye can't see itself), there are also specific experiences related to the nature of mind that evade ordinary mind. A simple example: in his boo The Crystal and the Way of Light, Namkhai Norbu describes one of his meditational experiences where he sees 5 spheres of light in one bigger sphere. In this experience, there is no space between the spheres but this seemed perfectly natural. After he finished the practice session, he sat and tried to draw it and after several attempts realized it's impossible. There are many similar accounts.