Shiva Purana
नियोगः प्रदेश सर्वं कुंडं कुर्याद्विचक्षणः ॥ स्वनाभ्यंतःस्थितं वह्निं तद्रंध्राद्विस्फुलिंगवद् ॥ १६ ॥
A wise person should make the entire pot of Niyoga in the region. The fire within his nose was like a spark from his hole.
english translation
niyogaH pradeza sarvaM kuMDaM kuryAdvicakSaNaH ॥ svanAbhyaMtaHsthitaM vahniM tadraMdhrAdvisphuliMgavad ॥ 16 ॥
hk transliteration by Sanscript