https://www.youtube.com/watch?v=DkbTBwKaLKQ If one knows Sanskrit well then one can easily understand this work, Paramārthastavaḥ of Sri. Nāgārjuna (this work is not as popular as Prajñāpāramitahṛdaya sutra, yet this is also a beautiful one) - This was written in such a simple Sanskrit, even the non-scholars could relate to it at that time. Buddhism grew big in India only after Sri. Nāgārjuna. It is also easy to understand that including Sri. Siddhārtha Gautama Buddha and Sri. Nāgārjuna - all of them are agnostic and not really atheistic. The actual "Vāda" (theory) Sri. Nāgārjuna propagated was "Sarva-dharma-śūnya-vāda" - over time it was known more as "śūnya-vāda" and people started misinterpreting it as atheistic. https://www.youtube.com/watch?v=DkbTBwKaLKQ