No, no, go not to Lethe, neither twist 
       Wolf's-bane, tight-rooted, for its poisonous wine;
   Nor suffer thy pale forehead to be kiss'd
       By nightshade, ruby grape of Proserpine;
           Make not your rosary of yew-berries,
       Nor let the beetle, nor the death-moth be
           Your mournful Psyche, nor the downy owl
   A partner in your sorrow's mysteries;
       For shade to shade will come too drowsily,
           And drown the wakeful anguish of the soul.

   But when the melancholy fit shall fall
       Sudden from heaven like a weeping cloud,
   That fosters the droop-headed flowers all,
       And hides the green hill in an April shroud;
   Then glut thy sorrow on a morning rose,
       Or on the rainbow of the salt sand-wave,
           Or on the wealth of globed peonies;
   Or if thy mistress some rich anger shows,
       Emprison her soft hand, and let her rave,
           And feed deep, deep upon her peerless eyes.

   She dwells with Beauty--Beauty that must die;
       And Joy, whose hand is ever at his lips
   Bidding adieu; and aching Pleasure nigh,
       Turning to poison while the bee-mouth sips:
   Ay, in the very temple of Delight
       Veil'd Melancholy has her sovran shrine,
           Though seen of none save him whose strenuous tongue
       Can burst Joy's grape against his palate fine;   
   His soul shalt taste the sadness of her might,
           And be among her cloudy trophies hung. 

- John Keats

The following is the original first stanza, which Keats removed from the beginning of the poem before publication:

Though you should build a bark of dead men's bones,
And rear a phantom gibbet for a mast,
Stitch creeds together for a sail, with groans
To fill it out, bloodstained and aghast;
Although your rudder be a Dragon's tail,
Long sever'd, yet still hard with agony,
Your cordage large uprootings from the skull
Of bald Medusa: certes you would fail
To find the Melancholy, whether she
Dreameth in any isle of Lethe dull.