The Collaborative International Dictionary of English v.0.48:

Diapasm \Di"a*pasm\, n. [L. diapasma, Gr. ?, fr. ?; dia` through
   + ? to sprinkle: cf. F. diapasme.]
   Powdered aromatic herbs, sometimes made into little balls and
   strung together. [Obs.]
   [1913 Webster]