Shiva Purana
तीरं गत्वा तु गंडूषान्षोडशाचमनं द्विधा ॥ प्राणानायम्य च पुनः प्रणवं द्व्यष्टसंख्यया ॥ १४ ॥
He shall come to the bank, gargle sixteen times, perform Ācamana twice and Prāṇāyāma sixteen times repeating the Praṇava.
english translation
tIraM gatvA tu gaMDUSAnSoDazAcamanaM dvidhA ॥ prANAnAyamya ca punaH praNavaM dvyaSTasaMkhyayA ॥ 14 ॥
hk transliteration by Sanscript