SB 3.11.9
dvadasardha-palonmanam
caturbhis catur-angulaih
svarna-masaih krta-cchidram
yavat prastha-jala-plutam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The measuring pot for one nadika, or danda, can be prepared with a six-pala-weight [fourteen ounce] pot of copper, in which a hole is bored with a gold probe weighing four masa and measuring four fingers long. When the pot is placed on water, the time before the water overflows in the pot is called one danda.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
It is advised herein that the bore in the copper measuring pot must be made with a probe weighing not more than four masa and measuring not longer than four fingers. This regulates the diameter of the hole. The pot is submerged in water, and the overflooding time is called a danda. This is another way of measuring the duration of a danda, just as time is measured by sand in a glass. It appears that in the days of Vedic civilization there was no dearth of knowledge in physics, chemistry or higher mathematics. Measurements were calculated in different ways, as simply as could be done.