Shiva Purana
ते चाष्टमूर्तयः कल्प्याः पूर्वादिपरितः स्थिताः ॥ चत्वारश्चाथ वा दिक्षु स्वध्येतारस्सजापकाः ॥ २३ ॥
They are to be imagined as having eight forms and are situated around the east and the west. Or four in the directions who are self-studying and chanting.
english translation
te cASTamUrtayaH kalpyAH pUrvAdiparitaH sthitAH ॥ catvArazcAtha vA dikSu svadhyetArassajApakAH ॥ 23 ॥
hk transliteration by Sanscript