“The world’s vast and strange, Hara, but no vaster and no stranger than our minds are. Think of that sometimes.”

Ch 28 : The Shallowest Sort of Mysticism
The Cream of the Jest (1917)
Context: I quite fixedly believe the Wardens of Earth sometimes unbar strange windows, that face on other worlds than ours. And some of us, I think, once in a while get a peep through these windows. But we are not permitted to get a long peep, or an unobstructed peep, nor very certainly, are we permitted to see all there is — out yonder. The fatal fault, sir, of your theorizing is that it is too complete. It aims to throw light upon the universe, and therefore is self-evidently moonshine. The Wardens of Earth do not desire that we should understand the universe, Mr. Kennaston; it is part of Their appointed task to insure that we never do; and because of Their efficiency every notion that any man, dead, living, or unborn, might form as to the universe will necessarily prove wrong.

Source: The Cream of the Jest (1917), Ch. 40 : Which Mr. Flaherty Does Not Quite Explain
Context: The Wardens of Earth sometimes unbar strange windows, I suspect — windows which face on other worlds than ours: and They permit this-or-that man to peer out fleetingly, perhaps, just for the joke's sake; since always They humorously contrive matters so this man shall never be able to convince his fellows of what he has seen or of the fact that he was granted any peep at all. The Wardens without fail arrange what we call — gravely, too — "some natural explanation."

Aeaea, Ch. 6
Space Chantey (1968)
Context: Do you not know that the underground lands are shared by many worlds? It is all one underground, a vast place, and it is but a trick on which globe one will surface on coming out. This is the reason that the inside of every world is so much vaster than the outside. You are fooled by the shape of these little balls on which things live and crawl; you see the universe inside out; you see the orbs as containing and not contained. I will teach you to see it right if you please me.

Source: Don Juan

Source: The Shadow of the Wind

Source: Across the Frontiers

Or, for that matter, as true.
Source: The Areas of My Expertise (2005), p. 18

Private notes, quoted in Herbert Butterfield, ‘Acton: His Training, Methods and Intellectual System’, in A. O. Sarkissian (ed.), Studies in Diplomatic History and Historiography in honour of G. P. Gooch, C.H. (1961), p. 194
Undated

"The Salutation", stanza 7; The Poetical Works of Thomas Traherne, B.D. (London: Bertram Dobell, 1903) p. 3.