The question makes reference to a horse being viewed as an untrustworthy historical source, but it gives no further information on the horse or its significance in history.
Furthermore, the validity of a source named "Pirates of pirates letter to Herod" is called into question, and it is emphasized that authorship, context, and aim are vital considerations when assessing historical sources. The letter's veracity is still questionable in the absence of precise information regarding its contents and context.
A historical source may be deemed untrustworthy if it exhibits prejudice, lack of trustworthiness, a narrow point of view, or deliberate manipulation. Assessing sources for objectivity and accuracy is crucial.