Thomas was a most laborious copyist: missals, books of devotion and a famous MS. Bible were written by him.
But no mere copyist or verbal translator could have attained that result.
It seems difficult also to believe that Map's name should be so constantly connected with our Arthurian tradition without any ground whatever; though it must be admitted that he himself never makes any such claim - the references in the romances are all couched in the third person, and bear no sign of being other than the record by the copyist of a traditional attribution.
These errors arise from the default of the scribe or copyist, and, in the case of printed books, the compositor.'
according to the degree in which the volition of the copyist is absent or present, as involuntary or mechanical, semivoluntary and voluntary; or again as they affect single signs (letters, figures or symbols), words, lines or even larger units such as sentences or paragraphs.