The Ganesha Atharvashirsha — sometimes called the Ganapati Upanishad — is a remarkable text. It begins as a hymn to Ganesha but quickly reveals that Ganesha is not simply an elephant-headed deity: he is Brahman itself, the ground of all existence.
'You are the directly perceivable truth' (pratyaksham tattvam asi) — Ganesha is being identified with Reality as it actually is, here and now, directly knowable. He is creator, sustainer, and dissolver — the three functions associated with Brahma, Vishnu, and Shiva — all in one.
The closing line — 'You are the Atman, always, directly' — brings this to its peak: Ganesha is not outside us, not distant. He is our own innermost Self.