Through Hindu religious scriptures were/ are passed through oral traditions to succeeding generations,some of them especially relating to Tantra and rare stothras, Grammar, Sanskrit literature were later transcribed in the form of manuscripts.They are, in general ,written on Palm leaves.Not only in Sanskrit but literature, philosophical , religious texts in Indian regional languages like Tamil were also written in Palm Leaves.Vedas, the most authentic scriptures of Hinduism was transmitted orally. However, these were also written during later periods and the Manuscripts of the Vedas ,at least some of them are in Pune. I have written on this.

The Digitized copies  of The Rigveda Brahmanas: the Aitareya and Kausītaki Brāhmanas of the Rigveda are in American Libraries.

Manuscripts form an invaluable part of India’s documentary heritage. They capture our thoughts, achievements, experience and lessons learnt from history; in other words, they constitute our ‘memory.’ The National Mission for Manuscripts has taken the initiative to nominate Indian manuscripts for inclusion in UNESCO’s Memory of the World register. Under this programme, UNESCO provides recognition to the most valuable documentary heritage of the world and facilitates its preservation and universal access to it. Moreover, efforts are made to increase awareness of the significance of these records.

The Shaiva manuscripts in Pondicherry were awarded the status of UNESCO’s Memory of the World in 2005 in an application jointly submitted by the French Institute of Pondicherry, Centre for Ecole francaise d’Extreme-Oriente (EFEO) and the National Mission for Manuscripts.The Mission had submitted 2 nominations to UNESCO:

In 1938, the Library of Congress received a three-year grant from the Carnegie Corporation to establish a project for the development of Indic studies, which was the Library’s first initiative to collect South Asian materials systematically. This grant enabled the project’s director, Horace Poleman, to spend about a year in India between 1939 and 1940. Urgency moved him to collect both rare books and contemporary works on modern affairs, as the outbreak of World War II cast uncertainty on the future of obtaining publications from India and the rest of the region. Poleman’s trip resulted notably in the Library’s acquisition of a large number of Sanskrit manuscripts, such as the Vyavasthasarasangraha (a compendium of Hindu authorities on religious law), Sarasvatistotra (a hymn of praise to the Hindu goddess of learning and music Saraswati), and a copy of Raghunandana Bhattacarya’s Tithitattva (a treatise on Hindu rituals to be performed on specific lunar days) dated to 1628.

Sanskrit is one of the principal classical languages of ancient India. The word itself means something like “perfected,” “refined,” or “well put together” (sam – together, krta – done, made). Works in Sanskrit are found throughout Buddhist, Jain, and Hindu religious traditions. For many Hindus, it is a sacred medium of expression – the language of ancient scriptures such as the Vedas, Upanishads, and Bhagavad Gita. Many people are familiar with Sanskrit in the Devanagari script – the same script used for Hindi, Nepali and other modern vernaculars – but Sanskrit texts have also been written in other writing systems, (e.g., the Grantha in southern India, the Sharada in Kashmir). To get a sense of what the language sounds like, check out some samples of poetry and prose from contemporary Sanskrit authors in the Library’s South Asian Literary Recordings Project.

Sanskrit vowels and consonants with a guide to pronunciation, from H.H. Wilson’s “An Introduction to the Grammar of the Sanskrit Language,” 1841, Library of Congress general collections. Also freely available on HathiTrust.

Poleman was prepared for his acquisition trip to India. In addition to holding a doctorate in Sanskrit from the University of Pennsylvania, he had already authored a comprehensive census of Indic manuscripts in North American libraries. The range of manuscripts in the Library’s collection reflects his deep understanding of Sanskrit literature. The majority deal with religious subjects, like the Anantapuja (worship), Shraddhasankalpa (funerary rites), and Gayatrisahasranamastotra from the Rudrayamala (esoteric religion, or tantra). There are also smaller works from sections of the Padma Purana, Brahmanda Purana, and other puranas, or religious texts that tell the stories of Hindu gods and goddesses. Notable works on other topics are the Vaiyyakaranasiddhantaratnakara (grammar) and Sanketakaumudi (astrology).https://blogs.loc.gov/international-collections/2018/01/sanskrit-manuscripts-in-the-south-asian-rare-books-collection/

One can find rare manuscripts relating to Philosophy,Science, Astronomy, Astrology, Tantra Sastra, Grammar,..whole spectrum of Knowledge as acquired by Ancient India. These texts cover Hinduism,Jainism, Buddhism,Carvakas and Six systems of Indian Philosophy These texts are in Sanskrit,Pali.

A census of Indic manuscripts in the United States and Canada,Cite Record.
https://lccn.loc.gov/39001439
Poleman, H. I. (Horace Irvin), 1905-1965. A census of Indic manuscripts in the United States and Canada, compiled by H. I. Poleman. New Haven, Conn., American oriental society, 1938.
xxix, 542 p. 26 cm.
Z6605.I5 P7. Visit the following Link.https://catalog.loc.gov/vwebv/citeRecord?searchId=612&recPointer=0&recCount=25&searchType=1&bibId=1691194