The Collaborative International Dictionary of English v.0.48:

Long primer \Long" prim"er\n. (Print.)
   A kind of type, in size between small pica and bourgeois.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Primer \Prim"er\, n. [Originally, the book read at prime, the
   first canonical hour. LL. primae liber. See Prime, n., 4.]
   1. Originally, a small prayer book for church service,
      containing the little office of the Virgin Mary; also, a
      work of elementary religious instruction.
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            The primer, or office of the Blessed Virgin. --Bp.
                                                  Stillingfleet.
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   2. A small elementary book for teaching children to read; a
      reading or spelling book for a beginner.
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            As he sat in the school at his prymer. --Chaucer.
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   3. (Print.) A kind of type, of which there are two species;
      one, called long primer, intermediate in size between
      bourgeois and small pica [see Long primer]; the other,
      called great primer, larger than pica.
      [1913 Webster]

   Note: Great primer type.
         [1913 Webster]