The Collaborative International Dictionary of English v.0.48:

Polyoptron \Pol`y*op"tron\, Polyoptrum \Pol`y*op"trum\, n. [NL.,
   from Gr. poly`s many + ? seen.] (Opt.)
   A glass through which objects appear multiplied, but
   diminished in size. [R.]
   [1913 Webster]