Shiva Purana
उत्तमस्तु त्रिरुद्धातः षड्विंशन्मात्रकः परः ॥ स्वेदकंपादिजनकः प्राणायामस्तदुत्तरः ॥ २९ ॥
Uttama has three strokes and its duration is thirty-six Mātrās. Uttara is the Prāṇāyāma that causes perspiration and trembling of the body.
english translation
uttamastu triruddhAtaH SaDviMzanmAtrakaH paraH ॥ svedakaMpAdijanakaH prANAyAmastaduttaraH ॥ 29 ॥
hk transliteration by Sanscript