Truti
Srimad-Bhagavatam
SB Canto 3
It is calculated that if a second is divided into 1687.5 parts, each part is the duration of a truṭi, which is the time occupied in the integration of eighteen atomic particles.
SB 3.11.6, Translation and Purport: The time duration needed for the integration of three trasareṇus is called a truṭi, and one hundred truṭis make one vedha. Three vedhas make one lava.
It is calculated that if a second is divided into 1687.5 parts, each part is the duration of a truṭi, which is the time occupied in the integration of eighteen atomic particles. Such a combination of atoms into different bodies creates the calculation of material time. The sun is the central point for calculating all different durations.
SB 3.11.14, Purport:
One truṭi - 8/13,500 second