Shiva Purana
गुर्वासनाय नम इत्यासनं परिकल्पयेत् ॥ गुरोर्मूर्तिं च तत्रैव कल्प येदुपदेशतः ॥ ११ ॥
One should arrange a seat saying 'Om Guruvasanaya Namah' The idol of the spiritual master is also placed there according to the instructions of the Kalpa.
english translation
gurvAsanAya nama ityAsanaM parikalpayet ॥ gurormUrtiM ca tatraiva kalpa yedupadezataH ॥ 11 ॥
hk transliteration by Sanscript