"The True Path of the Ninja: The Definitive Translation of the Shoninki" is a translation of a medieval ninja document from Kishū province. In the Shoninki, the original author (a ninja by the name of Natori Masatake) describes some of the magics that were used by ninja during at the time. Magic amulets (paper with a spell written on it) were popular, and a few of the spells he included in the book were for luck and for protection from arrows.

https://www.worldcat.org/title/true-path-of-the-ninja-the-definitive-translation-of-the-shoninki/oclc/643081999&referer=brief_results