The Aleph by Jorge Luis Borges (1945)

Go down to the cellar, lie flat on the floor in the dark, and fix your eyes on the nineteenth step. There, the size of a small marble and faintly shimmering, sits a point that contains every other point in the universe. Look into it and you see the teeming sea and every ant on earth, a silvery cobweb at the centre of a black pyramid, the circulation of your own dark blood, all of it at once, occupying no space and overlapping nothing. The man who looks, a narrator named Borges, has climbed down here only because he loved the dead woman whose family keeps the house, and the cruelty is that the infinite hands him the proof of how little she loved him back. This is the ache the story is built on: the Aleph holds all of creation in one instant, and a sentence can only move one word after another, so to tell what he saw is to begin losing it. Two pages, and they carry more sky than novels ten times the length.