Manuscripts on the arts of the shinobi have only the simplest mention of astrological skills and the arts of astronomy, and assume that the reader should have a good understanding of these things. In particular, they have no mention of swordsmanship, horse-riding skills or other combat skills, because it was taken for granted that people would naturally train themselves in those areas. Simply looking at the shinobi scrolls limits our understanding of the full range of skills in which shinobi would have been proficient at. Most writings on the shinobi arts have only simplified information, and where it needs detailed explanations, the authors would write down "kuden" (passed down in oral traditions).