Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v2.c12.s5.26

v2.c12.s5.26

5. *The Nāḍivalaya* :—Procure a circular disc. Graduate its rim in ghaṭikās. Pass a rod through its centre perpendicular to the disc. When the rod is held, pointed to the pole, it will cast a shadow on the rim ; and from it the hour angle (natakāl) or its complement can be read. If this very disc is so fitted in a globe that the pole stick will pass through its centre and the terrestrial globe will occupy the central position in it, and if marks indicating ghaṭikās, rising of signs, and the sixfold division of signs (lagna ; horā ; dreṣkāṇa ; navāṃśa ; dvādaśāṃśa & triṃśāṃśa) are made on it, then the shadow cast by the stick will help in finding the time elapsed and the sixfold divisions.