The ritsuyo system strictly prohibited all outsiders (everybody, not only oracles and monks but also general civil servants and private citizens) except for the persons appointed as trainees at Onmyoryo to learn astronomy, onmyo, reki, or measuring hours, or to discuss the occurrence of disasters, unusual phenomenon or auspicious events, it also prohibited any equipment relating to astronomical observation and measuring time, or documents about the various arts of onmyo, to be removed from Onmyoryo, and it even forbade private individuals from owning any of the foregoing equipment or documents.
律令においては、陰陽寮の修習生に登用された者以外の一切の部外者（神官・僧侶はもちろん一般官僚から民間人に至るまでの全て）が、天文・陰陽・暦・時間計測を学び災異瑞祥を説くことを厳しく禁止しており、天文観測や時刻測定にかかわる装置ないし陰陽諸道に関する文献について、陰陽寮の外部への持ち出しを一切禁じ、私人がこれらを単に所有することさえ禁じられていた。