The Pali term "nesajjika" means «the one who has the habit to be seated».
"nissída" = "sitting posture"
The bhikkhu who takes up the habit to renounce to the lying posture, only adopting sitting, standing and walking postures, is called a "nesajjika". When this practice is conveniently done, with constancy and diligence, with the determination of not breaking it, we say that there is "nesajjikaýga " (state of mind arising out of renunciation to the lying posture).
For adopting this dhutaýga, it is convenient to pronounce the following phrase whether in Pali, whether in the language of one's choice...
«seyyaµ pa†ikkhipámi, nesajjikaýgaµ samádhiyámi.»
«I renounce to the lying posture, I will train into always remaining seated (at time of taking rest)»
According to restrictions, there do exist three kinds of practitioners of the nesajjika dhutaýga:
The noble practitioner of the nesajjika dhutaýga never does any of the following things, even while sleeping: 1) applying the back on something; 2) clasping the knees by means of a tissue; 3) clasping or maintaining one's knees by means of the hands or the arms.
The intermediate practitioner of the nesajjika dhutaýga adopts one of the three things that a noble practitioner rejects.
The ordinary practitioner of the nesajjika dhutaýga adopts two or three of the things rejected by the noble practitioner. He can put up a pillow behind his back, or sit on a chair whose upper back doesn't exceed an inclination of 45° or devoid of back.
In Buddha's time did the Mi¦ábhaya maháthera, who practised the nesajjika dhutaýga. This maháthera was offered a high quality bed by his dáyakas. The maháthera has trained into the development of vipassaná, while scrupulously keeping up his nesajjika dhutaýga. In a short while, he became an anágámi.
Thus, it is convenient that some bhikkhus, who practise the nesajjika dhutaýga, utilise all kinds of chairs and beds. As long as they do not lie down, they do not break their dhutaýga.
By practising the nesajjika dhutaýga, we can benefit with the following advantages...
Remark: the practice of a dhutaýga alone enables one to understand its advantages.
As soon as a practitioner of the nesajjika dhutaýga lies down and applies his head (on anything whatsoever), he breaks his dhutaýga.
During one of the three parts of the night, the practitioner of the nesajjika dhutaýga can stand up and walk. During this walk, the dhutaýga cannot be broken. Among the four postures – lying, seated, standing and walking –, the lying posture alone must be given up. During the night, the practitioner of this dhutaýga can therefore alternate between the three other postures. At time he is performing his walk, he keeps on developing his training (samatha or vipassaná). He can sleep while remaining seated during the two other parts of the night.
The devas who are harmful are afraid of an individual who remains seated well straight (in a meditative posture). When we practise this dhutaýga, we get rid of laziness, somnolence and feelings of attachment to the pleasure given by sleep. We benefit with a great víriya, we enjoy excellent conditions for training into kamma††hána (vipassaná or samatha). We can also develop the píti, which eradicates sensuous desires, we experience happiness.
For these reasons, some bhikkhus observe the nesajjika dhutaýga, which is a practice particularly propitious to the development and keeping up of víriya. The practitioners of this dhutaýga give a lot of prestige to the sásana.