Skandapurana 5.266.12

5.266.12

śucau deśe same puṇye pūrvottaraplave śubhe..
maṃḍapaṃ kārayedvidvān ramyaṃ ṣa़ośahastakam..
tanmadhye kārayedvediṃ caturhasta pramāṇataḥ.
yajamānasya hastena hastaikena samucchritām..12..

In a clean, level, holy, and auspicious place that slopes toward the east or north, / the learned man should have a charming pavilion constructed, measuring sixteen cubits. / In its center he should have an altar made, measuring four cubits, / and raised up by one cubit measured by the arm of the patron.