King Tissa ruled Anuradhapura for forty years from 247-207 B.C. He is considered to be the first consecrated King of Sri Lanka who was also a close friend of the contemporary Indian Emperor Asoka.
When Tissa sent envoys to Asoka with costly presents the Emperor in return conferred various honours on the envoys and on Tissa and sent everything that was required for the consecration of a king.
In addition, the envoys were asked to convey to Tissa that he (Asoka) had declared himself a lay disciple of Sakyamuni Buddha and that he would like Tissa himself to seek refuge in the three supreme gems.
At this consecration the King took the epithet Devanampiya meaning ‘beloved of the Gods’ that Asoka himself used, thus becoming Devanampiyatissa.
This was a great festival day in Sri Lanka. King Devanampiyatissa who was the ruling monarch declared a festival of water-sport for the inhabitants of the city and went hunting with his attendants. He ran up to Missaka mountain, and met the Thera there.
The Thera declared: “Recluses we are, O great King, disciples of the King of Dhamma (Buddha) Out of compassion for you alone have we come here from Jambudipa” (India). Hearing the words of the great Thera, the King dispelled his fear and remembering the message of his friend, King Asoka, and ascertaining that they were recluses, sat down near him.
The Thera, realising that the King was wise, after a brief discussion with him, preached the Culahatthipadopama Sutta to the monarch.
At the end of the sermon the King with forty thousand men, was established in the refuge.
The Venerable Bhikkhus headed by Mahinda Mahathera who arrived at Mihintalava from Vedisagiri in India met the king of Sri Lanka who was known as Devanampiyatissa on a full moon day of the month of Jettha. It was a festival day. The month of Jettha is the month of Poson (May-June).
Even today in Bihar the people call it the Jetthamasa. It is the name of an Asterisk that people pay reverence to the gods anticipating rain. The early ‘Aryan’ people who migrated to this country from North India must have continued this festival even after they arrived in Sri Lanka.
This may have been the reason why a water festival was held even during the visit of Thera Mahinda to Sri Lanka. The Thera Mahinda arrived in Sri Lanka at Missaka mountain. In the Sanskrit language Missaka means forest or grove. Panini points out that the Nandana Garden of the Vedic god Indra was also called Misraka.
The Thera Mahinda and his retinue arrived at Ambastala at Missaka mountain. The name Ambastala may have been used for that place for the simple reason that there were a large number of mango trees on the mountain.
Having spent a month in the city of Vedisa the Thera of great miraculous power on the Uposatha day of the month of Jettha (May-June) rose to the air from the monastery with the four Theras Sumana and Bhanduka the two laymen also came along with the Theras and stood on the Sila-peak in the noble and lovely Ambastala of the beautiful Missaka mountain.