sitting at ease
sukhāsana is the least ambitious of the crosslegged positions, meaning it is not likely to wreck anyone’s knees. Because the knees sit above the feet (ideally resting on the heels) the thighs slant upward slightly—not in itself a bad thing but it does mean it takes work to hold the lower back in and the body upright. In fact the position invites a relaxed slouch which is fine and natural for shelling peas, but not ideal for meditation. Even just thinking about the spine will likely trigger an impulse to sit tall. Sitting up on a support of some kind brings a more stable upright repose into the pose (and so makes it more like inherently supported lotus pose or siddhāsana). To exaggerate the difference find a grassy bank and try facing both uphill and downhill. Always good to bear in mind the floor is an arbitrary plane.
sukha + āsana (a + ā = ā)
sukha happy, comfortable, good, easy
sukha can mean ‘easy to do’ — as is evident in sukhāpa (sukha + āpa < āp get) ‘easily gained, easy to get’, or
sa bhaviṣyati sukham hantum
He will be easy to kill.
But more commonly, and probably here, it means at ease, not involved in effort and pain, the opposite of uneasy: in a calm or pleasurable mental state.
It is bound in a tight pair with its opposite:
sukha easy, pleasurable
duḥkha hard, painful
Every of these can be a basis for a verb:
sukhayati gladden, give pleasure to, delight
duḥkhayati sadden, give pain to, distress
su is related to Greek eu,
as in euphemism, euthanasia
duḥ is related to Greek dys,
as in dysfunction, dyslexia
(The breathy ḥ sound in Sanskrit, only ever at the end of words or syllables, is highly unstable depending on what follows, so duḥ dur dus dush are all possible expressions of the same word: dur-bandha ‘someone with difficult relatives.’)
Pali, one of the earlier textual languages for Buddhism, is a younger cousin to Sanskrit, marked in particular by simplified consonant clusters. Here duḥkha becomes dukka. Used as a noun this word presents the key notion of suffering or discontent.
But an alternate view is that dukka in Pali is in fact a reworking of a different Sanskrit word,
duḥ-stha ‘hard-standing, in a bad state’
and that then dukka is introduced into Sanskrit as duḥkha — which had not existed before but which now as it were pretends to be the origin of dukka. (Pali arises later than Sanskrit but both continue to be used side by side so the ‘later’ can influence the ‘earlier’.)
However according to the traditional view we have:
su + kha
duḥ + kha
khā is space, sometimes of an unbounded void (e.g. as a meditation focus) but originally a gap or hole and in particular in early use it refers to the hole in a chariot wheel through which the axle runs.
su + kha then means ‘that which has good space/a properly working wheel hole.’
In the Vedic poems sukha is exclusively used to describe a well-conditioned chariot (ratha, compare rotor; German Rad, wheel), one that rolls smoothly along. A recent translation renders this use of sukha as ‘well-naved’ (nave = hub), or in the superlative sukhatama ‘best-naved’! These are the chariots of the gods so obviously they are well tuned: duḥkha does not appear in the texts from this earliest stage of the language.
The idea that a non-creaky wheel would (later) supply the metaphor for the basic term for pleasurable mental states may seem a bit of a stretch: ‘I have a good hole (so my wheels run well)’ being a curious answer to ‘How are you?’ Hence the alternate view above: both su-stha and duḥ-stha (good-standing, bad-standing) exist in Sanskrit meaning more or less what sukha and duḥkha mean, but they are little used. It is the -kha pair that provide the pleasure-pain/good state-bad state opposition. This may be a sign of engagement with Buddhism.
The two terms get brought together into a compound of opposites:
pleasure and pain
agreeable and disagreeable sensations
the pleasure-pain system
Brought into relation like this, the words often address subjective experience rather than objective state: feeling good and feeling bad. They invoke the question what to do about pleasure and pain and the incentives they impose on us when they push us away from some things and pull us in toward other things. Do we just obey that system? A cultural and philosophical ideal, for both warriors and sages, is not to be governed by these stimuli but to treat pleasure and pain if as they were neutral facts (good luck with that!). In the mediterranean world this was the ambition of the Stoic sage. The opposite position is hedonism: that pleasure and pain are sufficient criteria for deciding what to do.
So in Bhagavadgīta 2.38 Krishna tells Arjuna he should go out and fight after having made himself indifferent to the difference between pleasure and pain:
sukha-duḥkhe same kṛtvā
making pleasure and pain the same
and likewise also he should erase the oppositions in the pairings jayājayau (jaya + ajaya) winning and not winning, and labhālabhau (labha + alabha) getting and not getting, even as he is to strive to his utmost to win and get. This combination — to be fully active externally but internally detached — is a kind of subversion of more thoroughgoing forms of world-rejection.
Curiously, although the metaphor of the smoothly running wheel is a dead one, chariots are not far away: Arjuna is sitting in a chariot for the whole of the Bhagavadgīta, and here when Krishna tells him to get up and fight he phrases it as ‘Yoke yourself to battle!’, like a horse to a chariot, using the same verb yuj that yoga (‘yoking’) is built off.
tato yuddhāya yujasva
so yoke yourself to battle
Sukhāsana is the comfortable pose and thankfully there’s no pose called duḥkhāsana, painful pose. But possibly every pose can be thought of as a sukhaduḥkhāsana, an easy/hard pose with careful balancing of comfort and a degree of discomfort.