He tapped his forehead.'These little grey cells. It is up to themöas you say over here.'

-Christie, Dame Agatha Mary Clarissa ne¤  e Miller
  The Mysterious  Affair at Styles, ch.10.

There was a little girl Who had a little curl Right in the middle of her forehead; And when she was good She was very, very good, But when she was bad, she was horrid.

-Longfellow, Henry Wadsworth
Attributed to Longfellow by Blanch Roosevelt Tucker Macchetta in The Home Life of Henry  W. Longfellow (1882).

Weep no more, woeful shepherds, weep no more, For Lycidas your sorrow is not dead, Sunk though he be beneath the watery floor, So sinks the day-star in the ocean bed, And yet anon repairs his drooping head, And tricks his beams, and with new spangled ore, Flames in the forehead of the morning sky: So Lycidas sunk low, but mounted high, Through the dear might of Him that walked the waves.

-Milton,John
  Lycidas, l.165^73.

L'amour, heurtant son front aveugle a'   tous les obstacles de la civilisation. Love, knocking its blind forehead against all of civilization's obstacles.

-Samuelson, Sir Sydney
  Indiana, preface.

Chumps always make the best husbands.When you marry, Sally, grab a chump. Tap his forehead first, and if it rings solid, don't hesitate. All the unhappy marriages come from the husbands having brains.What good are brains to a man? They only unsettle him.

-Plum
  TheAdventures of Sally, ch.10.