As explained elsewhere, Yog is not just a physical practice. It has a strong moral, ethical and spiritual basis; which is why it aims at such lofty goals such as liberation of the soul. If practised purely at the physical level, it degenerates into mere exercise and the practitioner denies himself much of the benefits that yog offers.
The pre-requisites are laid down in the Patanjali Yog Sutra, as the first two limbs of yog yam and niyam (moral restraint and ethical practices). After these practices have been implemented will the practictioner be able to obtain the full benefits of the next step, asan.
The transalations and commentary given below are based on the excellent book, The Original Yoga" by Shyam Ghosh.
Patanjali specifies five different moral restraints for the practictioner. These can also be interpreted in a positive manner, in the light of modern day practices
1. Ahims(a) -Non-violence
This is the first precept of any spiritual practice do no harm to any other living being. The important thing to note is that this does not just refer to physical acts of violence, but equally to violence in word and thought. This is a much more difficult proposition. You might not physically slap somebody but verbally abuse him. If he is in a stronger position than you, you might not have the guts to say or do anything, but yet mentally abuse him. According to Patanjali, all these behaviour is treated as himsa violence and is to be avoided. At the first stage itself we are shown that yog is more than a physical practice, but it involves subtler forms of action such as speech and thought. Ahimsa also has an impact on your diet it cannot be based on violence. More on this later
And why bother with Ahimsa? To quote Patanjali "when non-violence is established, hostility recoils in its presence". In such a mind, a violent thought cannot arise, let alone a hostile word or deed. (2:35)
A positive interpretation of Ahimsa would be "to have a loving touch". Not just abstain from doing violence to everyone you come into contact with, but have a very pleasant, loving, beautiful experience.
2. Saty(a) Truth
"A correct, uncoloured and well-weighed thought, when expressed faithfully in word or deed, means a restraint on the mind's tendency to bypass accuracy"
Patajali goes to to say "When truth is established, the means of action becomes un-necessary". (2:36) What he means is that truth requires no support or defence. The means of acting in a true and right fashion need not be sought out they will be clear as day.
This Yam can also be interpreted as "Being True to oneself' that is, acting in accordance to one's true self, and not doing what is not "in character" with yourself. Doing what you know you should do and nothing else.
3. Astey(a) Non-stealing
"Asteya is a curb on covetousness, which prompts one to grab, covertly or overtly, what belongs to others" Shyam Ghosh. Again the point is made that it does not make a difference if you steal openly or on the sly. Patanjali says that "when non-stealing is established, all treasures present themselves" (2:37). What is being indicated is that when there is no more desire for (material) goods, especially those which do not belong to you, the true (spiritual) treasures present themselves to you for the asking.
A modern interpretation could be "to be generous". Not just not to steal, but let your possessions, emotions, goodwill, thoughts flow freely. Life is a flow and when you go with the flow, wonderful things happen.
4. Brahmacharya (Continence)
Though the popular interpretation of brahmacharya is celibacy or continence, the actual word could be interpreted as "Brahma + acharan" which would mean one who is close to or at the feet of Brahma. Patanjali says "When Brahmacharya is established, virility is gained". (2:38). This is a pointer to the dissipative nature of excessive sexual activity that is so common today.
A modern interpretation of this Yam could be "inclusive relationships" which means you do not demand exclusivity in your relationships "you shall love me and me alone", but rather are willing to share and be a part of a larger whole.
5. A-parigrah (Non-receiving)
A rather high ideal of non-acceptance of gifts from others possibly meant as a further restraint on covetousness even for goods received as gifts. Perhaps the idea was that the yogi should not be under any obligation to anybody. Patanjali says that "when aparigraha is established, one gets awareness of past life events"! (2:39)
All these rules are intended to keep the yogi on the straight and narrow path. It is no use if the yogi, after coming down from his headstand, goes against any or all of these precepts! Patanjali also makes it abundantly clear that these yam(a)s are a "universal code of conduct, to be observed irrespective of kind, place, time or ocassion" (2:40). In other words, these cannot be observed conditionally rather they have to be unconditionally followed both in letter and spirit.
After dealing with the don'ts, Patanjali moves on to the do's in the Niyams or ethical observances.
1. Shouch - Purity
Naturally this does not refer to external purity alone which can be achieved by cleaning and bathing. Internal purity of thought is also important so your mind has pure thoughts of goodwill, friendliness etc. Patanjali explains that complete purity of mind means several things (2:41)
Cheerfulness not experiencing any regret but rather satisfaction and happiness
one-pointedness Ability to focus the mind's attention unwaveringly on an object
control of the senses refers to the mind's unquestioned superiority over the senses &
capacity to see the real self self-explanatory.
Patanjali goes on to say that once purity is established, there arises an aversion to the physical aspect of one's body as well as that of others. One stops looking at the body at the physical level alone, and devoting oneself to meeting physical needs directly and through others. Rather one becomes more spiritual, more wholistic.
2. Santosh (Contentment)
You must strive for higher ideals, while at the same time be contented and satisfied with your current lot. After all you have spent all your life and all your effort to get where you are, and that is to be respected. A dis-satisfied, discontent mind will never be at peace- always craving for more- a hindrance to spiritual practice. On the other hand, Patanjali says that "contentment leads to supreme joy", (2:42), that cannot be obtained by the enjoyment of external objects.
3. Tapas (Austerity)
The strict definition is austerity which envisages a simple living, renunciation of comforts, and often planned acceptance of discomforts to discipline oneself. Fasting or a vow of silence for a fixed period are common examples. Extreme and continued mortification of the body is obviously not called for as stated in the Bhagwad Gita, Yog is for the moderate person not for one who indulges in extreme practices. What is probably indicated is, sleeping on the floor, bathing in cold water, taking a minimum quantity of simple food and baring the body to the rigours of the weather all of them designed to strengthen the body and increase it's longevity. Patanjali says "Austerity purges impurities in the body, leading to mastery over the body and senses" (2: 43).
A modern interpretation of Tapas could be "sustained, in-depth, practice" by which alone a person gets mastery of a subject or object.
4. Sw-adhyay (Self-Study)
Self-study could mean self-directed study, as opposed to learning directly from a teacher, or also study of the self of course one has to know oneself before trying to know anyone else or anything else. Patanjali probably means study of the scriptures, since he says that by this method one gets "direct contact with the cherished deity"
5. Ishwar-Pranidhan (Surrender to God)
Surrender or complete devotion to God, or to the natural cosmic order, leads to Samadhi or liberation, says Patanjali. What further justification do we need?
The Hatha Yoga Pradeepika by Swami Swatmarama, a 16th Century Classic, lays down in no uncertain terms what the Yogi is supposed to eat and what he is not.
A moderate diet is recommended for a person desirous of having success in Yoga. [In fact, there is an Indian proverb, "A person who eats once a day is a yogi, twice a day a bhogi (one who enjoys life) and thrice a day a rogi (a diseased person)"
"A moderate diet is defined as taking pleasant and sweet food, leaving one-fourth of the stomach free, and offering up the act to Siva"
Commentary: Two parts of the stomach are to be filled with food, one part with water and one part empty (with air). Offering the act upto Siva (one of the Hindu Trinity) is that he should think that the eater is Siva and not himself"
"The following things are considered unsalutary to the yogi things that are sharp, sour, pungent, hot, certain nuts, leaves, oils, liquor, fish, flesh, curd, asafoetida, garlic"
"Diet of the following nature should be avoided as being unhealthy food that having once cooked has grown cold and is heated again, that has an excess of salt and sourness, that is indigestible or has certain kind of leaves mixed in it"
(Apparently the Yogis knew about the fermentation cooked food undergoes and the dangers of reheating such food after it has gone cold)
"The following things can be safely taken by the yogi wheat, rice, barley, milk, ghee, sugar candy, butter, honey, dry ginger, cucumber, the five green herbs, kidney beans and good water"
It would not be wise to disregard these admonitions and claim to be a true Hatha Yoga practioner
Further reading : Please see the articles listed in the column on the left.