Natyashastra
षट्पितापुत्रककृतः पञ्चपाणिरुदाहृतः । आद्यं प्लुतं द्वितीयं च लघु यत्राक्षरं भवेत् ॥ १८॥
That which is formed as Ṣaṭpitāputraka is called Pañcapāṇi. In it, the first syllable is prolonged (pluta), and the second syllable is short (laghu).
english translation
SaTpitAputrakakRtaH paJcapANirudAhRtaH । AdyaM plutaM dvitIyaM ca laghu yatrAkSaraM bhavet ॥ 18॥
hk transliteration by Sanscript