Shiva Purana
समाकुंच्याभ्यसेद्योगी रसनां तालुकं प्रति ॥ किंचित्कालांतरेणैव क्रमात्प्राप्नोति लंबिकाम्॥ ३५॥
The Yogin shall practise curving the tongue towards the palate. After sometime be can carry it to the uvula.
english translation
samAkuMcyAbhyasedyogI rasanAM tAlukaM prati ॥ kiMcitkAlAMtareNaiva kramAtprApnoti laMbikAm॥ 35॥
hk transliteration by Sanscript