The Manusmriti - if you ignore the social aspects of it has a calculation for the age of the universe. The very first chapter has it. I think it computes to about 12 billion years - close to what modern science brings it out to be.
My interest is the first chapter where he elaborates on the chronology of the universe.
One of the best explanations of Mantras and meditation are by Dr Robert Svoboda (for any audience more familiar with English than Sanskrit/hindi). Granted he trained under an Aghori which isn’t traditionally the path most folks would take. But his explanations are exemplary.