Ramayana
राक्षसेन्द्रा गिरिनिभाः शरैः शक्त्यृष्टितोमरैः । निरुछ्वासं हरिं चक्रुः प्राणायामा इव द्विजम् ॥ 7-7-6 ॥
the lords of the Rakshasas, huge as mountains, with arrows, spears, swords, and javelins rendered Hari breathless, as the breathing-exercises of pranayama render a twice-born man breathless.
english translation