Shiva Purana
रेचकाद्यं त्रयमिदं न द्रुतं न विलंबितम् ॥ तद्यतः क्रमयोगेन त्वभ्यसेद्योगसाधकः ॥ २५ ॥
The three, Recaka etc. shall not be done hurriedly or slowly. The practiser of Yoga shall adopt them gradually with restraint.
english translation
recakAdyaM trayamidaM na drutaM na vilaMbitam ॥ tadyataH kramayogena tvabhyasedyogasAdhakaH ॥ 25 ॥
hk transliteration by Sanscript