The Collaborative International Dictionary of English v.0.48:

Cangue \Cangue\ (k[a^]ng), n. [Written also cang.] [F. cangue,
   fr. Pg. canga yoke.]
   A very broad and heavy wooden collar which certain offenders
   in China are compelled to wear as a punishment.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

cangue
    n 1: an instrument of punishment formerly used in China for
         petty criminals; consists of a heavy wooden collar
         enclosing the neck and arms