The Collaborative International Dictionary of English v.0.48:

Assay \As*say"\, n. [OF. asai, essai, trial, F. essa. See
   Essay, n.]
   1. Trial; attempt; essay. [Obs.] --Chaucer.
      [1913 Webster]

            I am withal persuaded that it may prove much more
            easy in the assay than it now seems at distance.
                                                  --Milton.
      [1913 Webster]

   2. Examination and determination; test; as, an assay of bread
      or wine. [Obs.]
      [1913 Webster]

            This can not be, by no assay of reason. --Shak.
      [1913 Webster]

   3. Trial by danger or by affliction; adventure; risk;
      hardship; state of being tried. [Obs.]
      [1913 Webster]

            Through many hard assays which did betide.
                                                  --Spenser.
      [1913 Webster]

   4. Tested purity or value. [Obs.]
      [1913 Webster]

            With gold and pearl of rich assay.    --Spenser.
      [1913 Webster]

   5. (Metallurgy) The act or process of ascertaining the
      proportion of a particular metal in an ore or alloy;
      especially, the determination of the proportion of gold or
      silver in bullion or coin.
      [1913 Webster]

   6. The alloy or metal to be assayed. --Ure.
      [1913 Webster]

   Usage: Assay and essay are radically the same word; but
          modern usage has appropriated assay chiefly to
          experiments in metallurgy, and essay to intellectual
          and bodily efforts. See Essay.
          [1913 Webster]

   Note: Assay is used adjectively or as the first part of a
         compound; as, assay balance, assay furnace.
         [1913 Webster]

   Assay master, an officer who assays or tests gold or silver
      coin or bullion.

   Assay ton, a weight of 29,1662/3 grams.
      [1913 Webster]