Natyashastra
उल्लोप्यके सदा योज्य ऊहापोहविशारदैः । प्रकरी वस्तु षण्मात्रं पाताश्चैकान्नविंशतिः ॥ २६९॥
In the Ullopyaka, the Prakari should always be applied by those skilled in adaptation and improvisation. The Vastu of the Prakari consists of six Matras and nineteen Patas.
english translation
ullopyake sadA yojya UhApohavizAradaiH । prakarI vastu SaNmAtraM pAtAzcaikAnnaviMzatiH ॥ 269॥
hk transliteration by Sanscript