Agniveshyagrihyasutra 2.3.1.3

2.3.1.3

pañcaprasthaṃ śuci śuklaṃ sikatamanārdraṃ vivicya sthaṇḍilaṃ kṛtvā samacaturaśramaratnimātram udakprākpravaṇaṃ prādeśamātraṃ vrīhibhirdakṣiṇataḥ prācīṃ lekhāṃ likhati evaṃ madhyamamevamuttarataḥ \

Having sifted pure, white, non-moist sand to the amount of five prasthas, having made a sacrificial ground, square, measuring an aratni, sloping toward the northeast, measuring a span, he draws a line to the east on the south with grains of rice; likewise in the middle; likewise on the north.