Translators note: the following is an extract from the continuing translation I am making of parts of the Extended Mahāvaṁsa, together with Prince Tissa’s verses from the Theragāthā, specially translated for this post.
(Extended Mahāvaṁsa 462-479 = Mhv. 154-172)
One day [Asoka’s brother] Prince Tissa went hunting and saw deer sporting in the wilderness, and having seen that he thought thus: “Even the deer who live on grass enjoy the wilderness, will not the monks who live on pleasant food also enjoy themselves?” He went to his house and informed King Asoka of his thought.
To teach him, for seven days, Asoka gave him sovereignty: “You can experience sovereignty for seven days, young man, after that I will kill you,”  so said the Master of the Earth.
With the passing of seven days, he said: “Why are so you wasted away?” “Through fear of death,” he replied; and the King spoke again, saying: “Thinking: ‘After seven days I will die,’ you did not enjoy them, how will the strivers enjoy themselves when they always contemplate death?”
When his brother had spoken thus he gained faith in the Dispensation, and in time having gone hunting again, he saw the restrained Elder Mahādhammarakkhitaṁ,  pollutant-free, being fanned with a Sāl branch by a Nāga: “When will I live in the wilderness like this Elder, having gone-forth in the Victor’s Dispensation?” thought the one with wisdom.
The Elder, in order to instill faith, after rising into the sky and going to Asoka’s monastery, stood on the water of the pool. After placing the robes he wore in the sky and descending into the pond  he bathed his limbs.
The Prince, having seen this psychic power, gained great faith, and saying: “Today itself I will go forth!” the wise one made a wise decision.
He approached and respectively asked permission the King if he could go forth; unable to prevent him, after taking hold of him the Master of the Earth, surrounded by a great retinue, took him to his own monastery, and he went forth in the presence of the Elder Mahādhammarakkhita.
With him roughly four thousand other men also received the going-forth, but the exact number is not known. 
The King’s nephew called Aggibrahmā,  well-known as the husband of the King’s daughter Saṅghamittā, and their son who was known by the name of Sumana, asked permission from the King and also went forth with the Prince.
The Prince’s going-forth was in King Asoka’s fourth year, and increased the benefit of the multitude. Right there he received the higher ordination, and having the supporting conditions, while striving the Prince became a Worthy One, with the six psychic powers.
Ekavihāriyattheragāthā (Theragāthā 537-568)
The Verses of the Elder Lone-Dweller 
537. Purato pacchato vāpi aparo ce na vijjati.
If there is no one found in front or behind
atīva phāsu bhavati ekassa vasato vane.
that is very comfortable for one who dwells alone in a wood.
538. Handa eko gamissāmi araññaṁ Buddhavaṇṇitaṁ,
Well, I will go alone to the wilderness praised by the Buddhas,
phāsu ekavihārissa pahitattassa bhikkhuno.
which is comfortable for the monk who dwells alone, who is resolute.
539. Yogī-pītikaraṁ rammaṁ mattakuñjarasevitaṁ,
The delightful forest, which brings joy to yogis, where rutting elephants live,
eko attavasī khippaṁ pavisissāmi kānanaṁ.
I will quickly enter, and there will I dwell by myself alone.
540. Supupphite Sītavane sītale girikandare,
In the cool blossoming Cool Wood, which has mountain caves,
gattāni parisiñcitvā, caṅkamissāmi ekako.
after washing my limbs, I will walk (in meditation) alone.
541. Ekākiyo adutiyo ramaṇīye mahāvane –
Alone, without a second, in the delightful great wood –
kadāhaṁ viharissāmi, katakicco anāsavo?
when will I live (so), having fulfilled my duties, without pollutants?
542. Evaṁ me kattukāmassa adhippāyo samijjhatu,
May the intention succeed for the one who has this desire,
sādhiyissām’ ahaṁ yeva, nāñño aññassa kārako.
I myself will accomplish it, no-one can act on behalf of another.
543. Esa bandhāmi sannāhaṁ pavisissāmi kānanaṁ,
I am bound in armour,  I will enter the forest,
na tato nikkhamissāmi, appatto āsavakkhayaṁ.
I will not depart from there without the destruction of pollutants attained.
544. Mālute upavāyante sīte surabhigandhike
While the breeze blows cool, fragrant and perfumed
avijjaṁ dālayissāmi, nisinno nagamuddhani.
I will burst apart ignorance, sitting on the mountain top.
545. Vane kusumasañchanne pabbhāre nūna sītale
In a flowery wood, on the cool mountain slope,
vimuttisukhena sukhito, ramissāmi Giribbaje.
I will delight in Giribbaja,  happy with freedom’s bliss.
546. Sohaṁ paripuṇṇasaṅkappo, cando pannaraso yathā,
I am one whose aspiration, like the moon on the fifteenth day, has come to fulfillment,
sabbāsavaparikkhīṇo, natthi dāni punabbhavo ti.
with all pollutants completely destroyed, now there is no rebirth.
Itthaṁ sudaṁ āyasmā Ekavihāriyo Thero gāthāyo abhāsitthā ti.
The verses that the venerable Elder Lone Dweller spoke.
- As he had already killed ninety-nine of his brothers, this must have sounded very threatening. ↩
- The Elder is one of the Asokan missionaries, who converted Maharasthra. ↩
- Monks are allowed three covers for their bodies: their robes, a fire-house and a body of water. See Vinaya Cullavagga, Ch.5,16,2. ↩
- A curious admission, as the numbers never seem to be realisitic anyway. ↩
- Although I cannot find more information on Aggibrahmā, it appears he must have been Tissa’s son, as it is inconceivable that Asoka, who had killed all his rivals to the throne, except Tissa, would marry his daughter to one of his rival’s sons. ↩
- This is the name by which Tissa was known when he had become a monk. ↩
- The armour of virtue is meant, of course. ↩
- The ancient capital of Magadha, near to Rājagaha. ↩