In Greek mythology, the Pierian Spring of Macedonia was sacred to the Muses. As the metaphorical source of knowledge of art and science, it was popularized by a couplet in Alexander Pope's poem "An Essay on Criticism" (1709): "A little learning is a dang'rous thing;/Drink deep, or taste not the Pierian spring."
The Pierian spring is sometimes confused with the Castalian Spring.
Classical sources 
The sacred spring was said to be in Pieria, a region of ancient Macedonia, also the location of Mount Olympus, and believed to be the home and the seat of worship of Orpheus. The Muses "were said to have frolicked about the Pierian springs soon after their birth". The spring is believed to be a fountain of knowledge that inspires whoever drinks from it.
- "His animum succinge bonis: sic flumine largo
- plenus Pierio defundes pectore verba.”
- "Come! Gird up thy soul! Inspiration will then force a vent
- And rush in a flood from a heart that is loved by the muse!"
Lines 215 to 232 of Pope's poem read:
- "A little learning is a dang'rous thing;
- Drink deep, or taste not the Pierian spring:
- There shallow draughts intoxicate the brain,
- And drinking largely sobers us again.
- Fir'd at first sight with what the Muse imparts,
- In fearless youth we tempt the heights of Arts,
- While from the bounded level of our mind
- Short views we take, nor see the lengths behind;
- But more advanc'd, behold with strange surprise
- New distant scenes of endless science rise!
- So pleas'd at first the towering Alps we try,
- Mount o'er the vales, and seem to tread the sky,
- Th' eternal snows appear already past,
- And the first clouds and mountains seem the last;
- But, those attain'd, we tremble to survey
- The growing labours of the lengthen'd way,
- Th' increasing prospects tire our wand'ring eyes,
- Hills peep o'er hills, and Alps on Alps arise!"
In Greek mythology, it was believed that drinking from the Pierian Spring would bring you great knowledge and inspiration. Thus, Pope is explaining how if you only learn a little it can "intoxicate" you in such a way that makes you feel as though you know a great deal. However, when "drinking largely sobers" you, you become aware of how little you truly know.
Later references 
In his poem "Hugh Selwyn Mauberley," Ezra Pound refers to Pierian "roses" in a critique of the cheap aesthetic of his time, which in his opinion has replaced a true appreciation of art and knowledge:
"Conduct, on the other hand, the soul
'Which the highest cultures have nourished'
To Fleet St. where
Dr. Johnson flourished;
Beside this thoroughfare
The sale of half-hose has
Long since superseded the cultivation
Of Pierian roses."
Henry Miller also made mention of it in his MOLOCH.
- Orpheus and Greek Religion (Mythos Books) by William Keith Guthrie and L. Alderlink, 1993, ISBN 0-691-02499-5, page 62
- Classical Mythology in Literature, Art, and Music (Focus Texts: For Classical Language Study) by Philip Mayerson,2001, page 82: "... the Muses who were said to have frolicked about the Pierian springs soon after their birth. The Castalian spring on Mount Parnassus ..."
- E.C. Marchant, Commentary on Thucydides: Book 2,Πιερίας—between Mt. Olympus and the Thermaic Gulf, the original home of the muses and birth-place of Orpheus.