Virtue's his path; but sometimes 'tis too narrow For his vast soul; and then he starts out wide, And bounds into a vice.

-Dryden,John
  Of  Antony.  All for Love, or The World Well Lost, act1.

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.

He turned the old one-stringed instrument into a many- chorded lyre† W.G. discovered batting; he turned its many narrow straight channels into one great winding river.

-Ranjitsinhji, Prince
  Of W G Grace.TheJubilee Book of Cricket.

Where the satyrs are chattering, nymphs with their flattering Glimpse of the forest enhance All the beauty of marrow and cucumber narrow And Ceres will join in the dance.

-Sitwell, Dame Edith Louisa
  Fa c° ade,'Tarantella'.

Here is all straight and narrow as a tomb Oh shut me not within a little room.

-Smith, Stevie (Florence Margaret)
  Harold's Leap,'The Commuted Sentence'.