The Collaborative International Dictionary of English v.0.48:

Ternary \Ter"na*ry\, n.; pl. Ternaries.
   A ternion; the number three; three things taken together; a
   triad.
   [1913 Webster]

         Some in ternaries, some in pairs, and some single.
                                                  --Holder.
   [1913 Webster]