Yaṣṭi-yantra

 (graduated tube, cylindrical stick) was an instrument used by early Indian astronomers.

It is one of Lalla's 12 instruments of astronomy.

Ãryabhaṭa describes it thus: it's length was the diameter of an associated circle, and it was held at center towards the sun. It was the hypotenuse. With it, one could find the ghaṭīs elapsed since sunrise.

Lalla also describes holding it as a hypotenuse, also using a sanku. He describes a method by which to use it to find altitude, zenith distance, and bāhu. In another operation he finds the equinoctial midday shadow. There is also mentioned a method for finding longitude & distances between planets.