To divide a cube into two other cubes, a fourth power or in general any power whatever into two powers of the same denominationabovethesecond isimpossible, and Ihave assuredly found anadmirable proof of this, but the margin is too narrow to contain it.

-Fermat, Pierre de
Scribbled note in the margins of his copy of Diophantus's Arithmetica. He did not live to provide the promised proof, and the conjecture became famous as Fermat's Last Theorem. In 1993  Andrew Wiles, a British mathematician, claimed to have discovered the proof.

I think you will like them, when you shall see them on a beautiful quarto page, where a neat rivulet of text shall meander through a meadow of margin.

-Sheridan, Richard Brinsley
  Sir Benjamin Backbite, of his love elegies to Maria. The School for Scandal, act1, sc.1.

I cannot rest from travel: I will drink Life to the lees: all times I have enjoyed Greatly, have suffered greatly, both with those That loved me, and alone; on shore, and when Through scudding drifts the rainy Hyades Vext the dim sea: I am become a name; For always roaming with a hungry heart Much have I seen and known; cities of men And manners, climates, council, governments, Myself not least, but honoured of them all; And drunk delight of battle with my peers, Far on the ringing plains of windyTroy. I am part of all that I have met; Yet all experience is an arch wherethrough Gleams that untravelled world, whose margin fades For ever and for ever when I move. How dull it is to pause, to make an end, To rust unburnished, not to shine in use! As though to breathe were life.

-Tennyson
  Poems,'Ulysses' (published1842), l.6^24.

Launch your vessel, And crowd your canvas, And, ere it vanishes Over the margin, After it, follow it, FollowThe Gleam.

-Tennyson
  'Merlin andThe Gleam', stanza 9, l.126^31.

Continuous as the stars that shine And twinkle on the milky way They stretched in never-ending line Along the margin of a bay: Ten thousand saw I at a glance, Tossing their heads in sprightly dance.

-Wordsworth,William
  'I wandered lonely as a cloud', stanza 2 (published1807).