One verse

Srimad Bhagavatam 4.1.21

4.1.21

तप्यमानं त्रिभुवनं प्राणायामैधसाग्निना । निर्गतेन मुनेर्मूर्ध्न: समीक्ष्य प्रभवस्त्रय: ॥ २१ ॥

tapyamanam tri-bhuvanam pranayamaidhasagnina nirgatena muner murdhnah samiksya prabhavas trayah

tapyamanam
while practicing austerities
tri-bhuvanam
the three worlds
pranayama
practice by breathing exercise
edhasa
fuel
agnina
by the fire
nirgatena
issuing out
muneh
of the great sage
murdhnah
the top of the head
samiksya
looking over
prabhavah trayah
the three great gods (Brahma, Visnu and Mahesvara).

While Atri Muni was engaged in these severe austerities, a blazing fire came out of his head by virtue of his breathing exercise, and that fire was seen by the three principal deities of the three worlds.