P.D. Ouspensky's Tertium Organum has this extract from Kant’s CPR in the starting chapter.

The entire book can be considered to be…

Mathematico-mystical variations on the Kantian theme

Nothing which is intuited in space is a thing in itself, and space is not a form which belongs as a property to things; but objects are quite unknown to us in themselves, and what we call outward objects arc nothing else but mere representations of our sensibility, whose form is space, but whose real correlate, the thing in itself, is not known by means of these representations, nor ever can be, but respecting which, in experience, no inquiry is ever made. . . .

The things which we intuit are not in themselves the same as our representations of them in intuition, nor are their relations in themselves so constituted as they appear to us; and if we take away the subject, or even only the subjective constitution of our senses in general, t hen not only the nature and relations of objects in space and time, but even space and time themselves disappear. . . .

What may be the nature of objects considered as things in themselves and without reference to the receptivity of our sensibility is quite unknown to us. We know nothing more than our mode of perceiving them. . . . Supposing that we should carry our empirical intuition [sensory perception] even to the very highest degree of clearness, we should not thereby advance one step nearer to the knowledge of the constitution of objects as things in themselves. . . .

To say, then, that all our sensibility is nothing but the confused representation of things containing exclusively that which belongs to them as things in themselves, and this under an accumulation of characteristic marks and partial representations which we cannot distinguish in consciousness, is a falsification of the conception of sensibility and phenomenization, which renders our whole doctrine thereof empty and useless.

Is Ouspensky a serious philosopher or a mystic or a wild fantasist I'll leave you to judge ?.
What can be agreed upon is that he uses a math-format...

As Fact? Truth?? Allegory??? I wont judge

---

^{Following @Conifold, I suggest you edit your question to change Judgement to Reason}