The emperor who was to perform Saiten purified himself in the ceremony called 'Zhaijie' in the special palace the day before, and went to the altar before the sunrise on the day of Saiten.
祭天に臨む皇帝は、前日から特別な宮殿で「斎戒」という身を清める儀式を受け、翌日陽も昇らない早朝から壇に向かう。