The public and ritual nature of liturgical services implies the necessity
of correct postures, gestures, and movements from one area to another.
Because of this, a complex set of directives came into being to aid in
the performance of the liturgy. In addition, one needed to judge the shifting
relationship between the fixed feasts of the sanctorale,
always occurring on the same calendar day, and the moveable feasts of
the temporale. These
directions for ranking feasts and for directing gestures are termed "rubrics"
from the Latin rubrum meaning "red" since they were frequently
written in red ink, or underlined in red, to distinguish them from the
words of the service itself. "Rubric" was, naturally enough,
also the word used for what we would call a chapter heading. One of the
first challenges in printing liturgical books was the combination of red
and black ink on a given page when "rubrics" were called for
not only to signal textual divisions, but also to give immediate visibility
to the "stage directions" and to the ranking of feasts. When
all the prescriptions for celebration of the liturgy are gathered into
a single volume, that book is termed an ordinal. If a book contains only
the directions for sacraments administered by a bishop, it is called a
pontifical. Over time, the ceremonial was studied by authors who attempted
to explain its allegory and codify its practice; the most complete of
such treatises was composed in 1286 by Guilelmus Durandus of Mende, the
Rationale divinorum officiorum.