Shiva Purana
मण्डलानि च तेष्वन्तः पुष्पाण्याधाय पीठवत् ॥ ॐ ह्री मित्युक्त्वाग्निरूपान्तामतिवाहिकदेवताम् ॥ ७ ॥
They placed flowers inside the circles like a seat Saying 'Om Hri', he worshiped the deity in the form of fire.
english translation
maNDalAni ca teSvantaH puSpANyAdhAya pIThavat ॥ OM hrI mityuktvAgnirUpAntAmativAhikadevatAm ॥ 7 ॥
hk transliteration by Sanscript