Nagarjuna :  Often called The Second Buddha, Arya  Nagarjuna (2nd century CE) was from a wealthy South Indian Brahmin family.  He is considered a terton (hidden-text revealer) as well as a philosopher.  It is said that the Buddha prophesied that someone would come after him who would clear up any confusion regarding Buddha-dharma. 

('After I, the Tathagata, have passed away And 400 years have elapsed A bhiksu, "The Naga", shall appear, of Great faith and benefit to the teaching. He shall achieve the stage of Great Joy And for 600 years remain living....)

Nagarjuna is considered to be that person.  He was an Indian master of philosophy and a tantric siddha. He was also  one of the Eight Vidyadharas; receiver of the tantras of Lotus Speech such as Supreme Steed Display. He is said to have taken birth in the southern part of India around four hundred years after the Buddha’s nirvana. Having received ordination atNalanda Monastery, he later acted as preceptor for the monks. . He  had erected pillars atBodhgaya  and stone walls to protect the Bodhi Tree and constructed 108 stupas. From the realm of the nagas he  had brought back the extensive Pajnaparamita scriptures.In someMahāyāna traditions, Nāgārjuna is regarded as a second buddha.

He was the life pillar for the Mahayana, but specifically he was a major exponent of the Unexcelled Vehicle of Vajrayana. Having attained realization of Hayagriva, he transmitted the lineage to Padmasambhava.

He knew alchemy, stayed alive for six hundred years and transformed ordinary materials into gold in order to sustain the sangha.

Textual masterpieces like "Ras Ratnakar," "Rashrudaya" and "Rasendramangal" are his renowned contributions to the science of chemistry. Where the medieval alchemists of England failed, Nagarjuna had discovered the alchemy of transmuting base metals into gold.

Nagarjuna was also a practitioner of Ayurveda, or traditional Indian Ayurvedic medicine.He was  first who  described in the Sanskrit medical treatise entitled Sushruta Samhita (of which he was the compiler of the redaction), many of his unique conceptualizations, such as his descriptions of the circulatory system and blood tissue (uniquely described as rakta dhātu) and his pioneering work on the therapeutic value of specially treated minerals knowns as bhasmas, which earned him the title of the "father of iatrochemistry(both chemistry and medicine). According to ancient Indian doctor Dalhana, Buddhist monk Nagarjuna ,Bodhisattva of Nalanda Monastic University is the redactor (compiler) of the Sushrut Samhita,

As the author of medical books like "Arogyamanjari" and "Yogasar," he also made significant contributions to the field of curative medicine. Because of his profound scholarliness and versatile knowledge, he was appointed as Chancellor of the famous University of Nalanda. Nagarjuna's milestone discoveries impress and astonish the scientists of today.

 Learning Alchemy:

Once, a terrible famine broke out in Magadha and continued for twelve years.   Nagarjuna was asked  to provide for the monks of Nalanda who lacked all necessities. He  decided to find out how to make gold. He took two sandalwood leaves and, with the appropriate mantras, gave them the power to instantly transport a person to wherever he wished to go. Holding one leaf in his hand and concealing the other in the sole of his sandal, he traveled across the ocean to an island where a famous alchemist lived. Nagarjuna requested instructions in the making of gold. Now the alchemist realized that Nagarjuna must have come across the water by a secret technique, so hoping to acquire this secret he said, "Let us exchange either our crafts or our wealth." "We should exchange our crafts," answered Nagarjuna, and gave him the leaf he held in his hand. 

The alchemist, thinking that Nagarjuna was no longer able to leave the island taught him how to make gold. Then Nagarjuna, by means of the sandalwood leaf he had hidden in his sandal, returned to India. There he turned a lot of iron into gold and provided the whole Sangha with all their needs

One day he will again return:

There is a story regarding end of his life.................

Having mastered all these teachings Nagarjuna returned to see his parents .A boy, Kumara Saktiman, had earlier been born to the queen of King Udayibhadra. Years later, while the mother was presenting her son with a rare, fine garment ,boy told her: "Put this away for me. I shall wear it when it is time for me to rule the kingdom." "You shall never rule," replied his mother, "for the Acarya Nagarjuna has brought it about that your father and he will not die unless the Acarya does." The boy was so overcome with grief that his mother continued: "Don't cry so! The Acarya is a Bodhisattva, and if you ask him for his head he will not refuse. With that, your father will also die --- and you shall acquire the kingdom."

The child followed his mother's suggestion and Nagarjuna did indeed agree to give his head. Yet however much effort the boy used, his sword could not cut Nagarjuna's neck. The Acarya told the boy: "Long ago, while cutting some grass, I happened to kill an insect. The force of that misdeed remains with me still, and you can thus sever my head by using a blade of kusa grass." This the boy did, and so was able to cut off Nagarjuna's head. The blood which flowed from the wound turned to milk, and the following words issued from the dismembered head: "From here I depart toSukhavati heaven. In the future, I shall enter this body again."

The wicked prince cast the head away at several leagues' distance, fearing that it would once more join the body. Since the Acarya had attained the practice of rasayana, however, his head and body became stone-hard. The two are said to be coming nearer and nearer, one to the other, every year, in the end to be joined once more. Nagarjuna will then again perform great works for the benefit of the teaching and all living beings.

Evidences and memories:

As is written in the Manjusrimulakalpa, the Acarya Nagarjuna lived for a total of 600years:SIdha Nagarjuna is stated to be a brahmin by caste who belonged to Kanchi in south.It is descibed that Nagarjuna came fom Vidhrabha to south.many docuents reveal that he was active in south. Contary to  this.traditional,literary and archaelogical evidences found in Himachal Pradeshaffirm his stay in the region for a long period. Another cave sight associated with Nagarjuna is located in Kaysa disrict.This place is reverred as a seat of siddha Nagarjuna who excelled in vak-siddhi and rasa-siddhi.There exists a temple dedicated to Naga Siddha at Rajnagar at Chumba.The Siddha is no other than Siddha Nagarjuna.  Nagarjuna had four principal spiritual sons, Shakyamitra, Nagabodhi, Aryadeva, and Matanga, as well as three close sons, Buddhapalita, Bhavaviveka, and Ashvagosha.

(Note:To describe the life and contribution of such a personality is not possible in my part.I  have collected and assimilated some informations regarding this unique personalty of history as per my knowledge and data available with me.This is only a symbol of remembering him and not at all a biography.I  request  Respected Rambhakta Mishra Sir for his additional inputs.)