Shiva Purana
षोडशारस्य पत्राणि स्वराः षोडश तानि वै ॥ पूर्वादीनि क्रमादेतत्पद्मं कन्दस्य मूलतः ॥ ६६ ॥
The leaves of the sixteenth śāra are composed of sixteen vowels. This lotus, beginning with the former, is placed at the root of the tuber.
english translation
SoDazArasya patrANi svarAH SoDaza tAni vai ॥ pUrvAdIni kramAdetatpadmaM kandasya mUlataH ॥ 66 ॥
hk transliteration by Sanscript