The Meditation Hall is regulated with militaristic severity and precision to cultivate such virtues as humility, obedience, simplicity, and earnestness in the monkish hearts that are ever prone to follow indiscriminately the extraordinary examples of the old masters, or that are liable to put in practice in a crude and undigested manner the high doctrines of a Śūnyatā philosophy such as is expounded in the Prajñā-pāramitā class of Mahayana literature. A partial glimpse of such life we have already gained in the description of the table manners as above. VI There is a period in the monastic life, exclusively set apart for mental discipline, and not interrupted by any manual labour except such as is absolutely needed. It is known as great “Sesshin” (_Chê-hsin_)[f143][7.24] and lasts a week, taking place once a month during the season called the “Summer Sojourn” and the “Winter Sojourn.” The summer sojourn begins in April and ends in August, while the winter one begins in October and ends in February. “Sesshin” means “collecting or concentrating the mind.” While this period is lasting, the monks are confined at the Zendo, get up earlier than usual, and sit further into the night. There is a kind of lecture every day during the period. Text books are used, the most popular of which are _The Hekiganshu_ and _Rinzairoku_,[7.25] the two being considered the most fundamental books of the Rinzai School. _The Rinzairoku_ is a collection of sermons and sayings of the founder of the Rinzai Zen sect. _The Hekiganshu_, as has been noted elsewhere, is a collection of one hundred Zen “cases” or “themes” with critical annotations and poetical comments. It goes without saying that there are many other books used for the occasion. To an ordinary reader, such books generally are a sort of _obscurum per obscurius_. After listening to a series of lectures, he is left in the lurch as ever. Not necessarily that they are too abstruse, but that the reader is still wanting in insight into the truth of Zen.