In the Ikkamyōshu scroll, Dogen likens 'satori' to a shining pearl and says that even if a person doubts that he or she is not a Myōju (pearl), that in itself is already a 'Ikkamyōshu', and concludes by saying: 'The progress and retreat in the Black Mountain Cave (Kurozan Oniguro) is only an Ikkamyōshu (shining pearl).
(The activity of advancing and retreating in the midst of hesitation is nothing other than the manifestation of 'satori').
Kurozan Oniguro is a mountain with a hell beneath it, mentioned in the Abhidharma Treatise, and is said to be the abode of the demon god, which in turn refers to the state of being caught in the grip of afflictions. Here, Dogen says that the practice of advancing and retreating through trial and error in the midst of vexations is the very practice that embodies 修証一等Shusho Ittō (practice is itself embodiment of satori),and is nothing other than 'satori'. It is not that we are moving towards the goal of 'satori', but that we have already realised 'satori' at each moment of our practice in this wandering world, in the sense that we are 'lost and enlightened'.
If you were going to compare meditation to a thing (for purposes of description, education, poetry or whatever), what would you compare it to?
As for Silent illumination, I would say not-looking into a mirror
That's pretty abstract. What else have you got?
Nothing else, this was the first thing that came to my mind