=item * sigil - A short code to represent the manuscript. Required.
=item * text - An array of strings (words) that contains the text of the
-manuscript.
+manuscript. This should not change after the witness has been instantiated,
+and the path through the collation should always match it.
+
+=item * layertext - An array of strings (words) that contains the layered text,
+if any, of the manuscript. This should not change after the witness has been
+instantiated, and the path through the collation should always match it.
=item * source - A reference to the text, such as a filename, if it is not
given in the 'text' option.