English: The early Upanishads are scriptures of Hinduism.

The above image is from Aitareya Upanishad with commentary by Adi Shankara (c. 800 CE).

The bolded letters are the text, the light diacritics, any colored marks, light dashes and dots under the letters are coded markers found in Sanskrit manuscripts for readers and reciters, i.e. dandas separate the words/sentences/verses, avagrahas for various compounds, circles for the galitas, and the particle iti. Colored or light texts on the margins are either corrections, or they are commentaries of the owner or some scholar / citations / reference-by-incorporation of another ancient Hindu scholar's work.

Language: Sanskrit

Script: Devanagari

The manuscript was discovered in Varanasi (Kashi, Benares) – one of the largest colonial era source for ancient Sanskrit literature. Notably it was found in a Jain temple manuscript bhandara. It was bought by European collectors in the 19th-century. It is now preserved with the Cambridge University Sanskrit manuscript collection.

The photo above is of a 2D artwork of a text that is over 2,000 years old, from a manuscript that was produced in 1863 CE. Therefore Wikimedia Commons PD-Art licensing guidelines apply. Any rights I have as a photographer is herewith donated to wikimedia commons under CC 4.0 license.