अनेन हि प्रमाणेन कलाताललयान्वितः । कर्तव्यः पूर्वरङ्गस्तु त्र्यश्रोऽप्युत्थापनादिकः ॥ १४०॥
For this is the measure, the prelude should be accompanied by the arts, time and rhythm, and should also be triangular, beginning with the raising of the curtain.
english translation