Shiva Purana
रेचकादिषु योभ्यासो नाडीशोधनपूर्वकः ॥ स्वेच्छोत्क्रमणपर्यंतः प्रोक्तो योगानुशासने ॥ २६ ॥
The practice of Recaka shall begin with the purification of the veins and conclude with its voluntary exit as mentioned in the Yogānuśāsana.
english translation
recakAdiSu yobhyAso nADIzodhanapUrvakaH ॥ svecchotkramaNaparyaMtaH prokto yogAnuzAsane ॥ 26 ॥
hk transliteration by Sanscript