Well, the version Burns collected and the one on which he based his "polite" version went:

COMIN' THRO' THE RYE
  (Burns' bawdy text)
  
  O gin a body meet a body
  Comin' thro' the rye;
  Gin a body f**k a body
  Need a body cry.
    

     Comin' thro' the rye, my jo,
       An' comin' thro' the rye,
       She fand a staun o' staunin' graith
       Comin' thro' the rye.
    

Gin a body meet a body
  Comin' thro' the glen
  Gin a body f**k a body
  Need the warld ken.
    

Gin a body meet a body
  Comin' thro' the grain. 
  Gin a body f**k a body
  C**t's a body's aim.
    

Gin a body meet a body
  by a body's sel,
  When na body f**ks a body
  Wad a body tell
    

Mony a body meets a body
  They dare na weel avow
  Mony a body f**ks a body,
  Ye Wadna think it true.

From Merry Muses of Caledonia, Burns note: the discreet typography is as published. I think it's dumb, but I've left it because I'm not sure how Burns would have spelled either "fuck" or "cunt".