CC Madhya 24.156
prādeśa-mātraṁ puruṣaṁ vasantam
gadā-dharaṁ dhāraṇayā smaranti
kecit — some of them; sva-deha-antaḥ — within one’s own body; hṛdaya-avakāśe — in the cavity of the heart; prādeśa-mātram — with the measurement of six inches; puruṣam — the Supreme Personality of Godhead; vasantam — residing; catuḥ-bhujam — with four hands; kañja — a lotus flower; ratha-aṅga — a disc like the wheel of a chariot; śaṅkha — a conchshell; gadā-dharam — holding the club; dhāraṇayā — by such contemplation; smaranti — they remember.
“ ‘Some yogīs think of the Lord within their hearts as measuring about six inches. The Lord has four hands, in which He holds a conchshell, club, disc and lotus flower. Those who worship this form of Viṣṇu within the heart are called sagarbha-yogīs.’
This verse is from Śrīmad-Bhāgavatam (2.2.8).