Brihat Samhita
श्लक्ष्णां पताकां असितां विदध्याद् दण्डप्रमाणां त्रिगुणोच्छ्रितां च । आदौ कृते दिग्ग्रहणे नभस्वान् ग्राह्यस्तया योगगते शशाङ्के ॥ २४-०९ ॥
He shall, beforehand, ascertain and mark out the several points of the compass and, planting vertically a flag staff—the stick being straight and thrice the length of the cloth which shall be thin, fine and of black colour, he shall ascertain the direction of the wind at the time when the Moon enters the asterism of Rohiṇī.
english translation
zlakSNAM patAkAM asitAM vidadhyAd daNDapramANAM triguNocchritAM ca । Adau kRte diggrahaNe nabhasvAn grAhyastayA yogagate zazAGke ॥ 24-09 ॥
hk transliteration by Sanscript