Siddhar

The Siddhar (Tamil: Cittar from Tamil cittu meaning knowledge, singular Citta, Sanskrit siddha) are saints in India, mostly Shaiva, from Tamilakam, who professed and practised an unorthodox type of sādhanā (spiritual practices) to attain liberation. A siddha obtains yogic powers called siddhi by constant practice of certain yogic disciplines and tapasya. The siddhars can be compared to mystics in Western culture.

Historically, Siddhar also refers to the people who were early age wandering adepts that dominated ancient Tamil teaching and philosophy. They were knowledgeable in science, technology, astronomy, literature, fine arts, music, drama, dance, and provided solutions to common people in their illness and advice for their future. Some of their ideologies are considered to have originated during the First Sangam period.

Siddhars are people who are believed to control and transcend the barriers of time and space by meditation (Yoga), the use of substances called Rasayanas that transform the body to make it potentially deathless, and a particular type of Pranayama (breathing-practice). Through their practices they are believed to have reached stages of insight which enabled them to tune into the powers hidden in various material substances and practices.

Typically Siddhars were saints, doctors, alchemists and mystics all in one. They wrote their findings in the form of poems in the Tamil language, on palm leaves which are collected and stored in what are known as the "Palm leaf manuscripts". These are still owned by some families in Tamil Nadu and handed down through the generations, as well as being kept in public institutions such as universities in India, Germany, Great Britain and the United States.

...
Wikipedia