The word hatha symbolizes two aspects within the body, surya shakti, solar energy, and chandra shakti, lunar energy. The solar energy is associated with prana shakti, vital energy, and the lunar energy is associated with chitta shakti, mental energy. Hatha yoga balances these two energies. That is its purpose. You are alive due to the presence of these two energies within you. Due to prana shakti you experience the vitality in the body and due to chitta shakti you experience the activities of the mind. Thus, hatha yoga is the method to create synchronicity, harmony and balance between body and mind.
Traditionally, hatha yoga begins with the practices of shatkarmas, the six practices of physical cleansing. With the help of shatkarmas one can free the body of vikaras, disorders. This body is God's gift to you, but you do not use it properly. Rather, you misuse it. When you buy a car, it comes with an instruction manual which contains information about what you need to pay attention to in order to keep the car in good condition. It tells you the optimum volume of air the tyres need, the amount of fluid the brakes and clutch need, the amount of petrol the engine needs, and so on. If you do not pay attention to these things, the car won't run properly for long. The manual also states how often you need to service the car. If it is looked after regularly, then even when something goes wrong it will not take much to repair it. The same rules apply to the body.
The common philosophy followed today – "Eat, drink and be merry" – ruins the body. A healthy body, free from physical disorders, is acquired by practising physical restraint, not by misusing it. Restraint is lacking in people's lives today. No restraint is practised in eating or sleeping, activities or thoughts. This spoils the natural habits of the body and mind, resulting in the formation of blocks in the body, which manifest as disease.
Ayurveda discusses three doshas, humours, which cause three kinds of disorders in the body. As long as kapha, mucus, pitta, bile, and vata, wind, are in a state of balance, one is healthy. The moment any one of them becomes dominant, the body begins to experience ill health. This indicates that the body requires balance and restraint, the lack of which causes vikaras, disorders. The purpose of hatha yoga is to remove the vikaras and harmonize the body.
The first lesson in shatkarmas is neti. Neti removes disorders of the nose, eyes and ears, eases mental tension and provides energy to the brain. The practices of dhauti and basti remove disorders of the digestive system, gas, acidity and mucus, and clean out putrid material from the intestines. In this way, the practices bring about a complete cleansing of the body from the head to the anus.
You have never cleansed your body since you were born. You may have an external bath every day, but you never clean the insides of your body. You have never cleansed the digestive system since eating your first morsel of food, nor have you practised restraint in eating. The speciality of the digestive system is that whenever you eat something it releases digestive juices. The system does not see that you are eating a peanut or a pizza, the amount of digestive juices released is the same irrespective of what you eat. Therefore, those who keep munching the whole day long overstrain the digestive system and experience acidity, gas and indigestion.
This is why hatha yoga emphasizes dietary restraint. It is said, "Eat your breakfast like a king, eat your lunch like a common man and eat your dinner like a beggar." If such rules are followed, one will never fall sick. One will never experience digestive disorders and will remain healthy. By practising dietary restraint and cleansing the body from within, one can free it of all the accumulated dirt and disorders. When the body acquires a state of purity, the pranas are able to flow smoothly.
The first three shatkarmas, neti, dhauti and basti, free annamaya kosha, the food body or physical body, of its defects. The other three shatkarmas are kapalabhati, nauli and trataka, which help contain the agitations of the mind and bring it to a point of focus. Trataka controls the dissipations of the mind. Kapalabhati removes mental tensions. Nauli awakens the centre of prana in the body, manipura chakra.
Yoga begins with these practices, not with asana and pranayama. If you study traditional yoga and try to understand its comprehensive philosophy, you will discover that yoga begins with the shatkarmas. Thereafter, the practices of asana, pranayama, mudra and bandha are introduced. They are dynamic practices through which you can relieve the stiffness of the body and prepare it for higher yoga sadhanas.
Hatha yoga is perfected when one has complete control over prana shakti and chitta shakti. Symbolically, it has been stated that prana shakti flows through the right nostril and chitta shakti through the left nostril. The nadi, pranic channel, through which prana shakti flows is called pingala and the nadi through which chitta shakti flows is called ida. When the two are balanced, the flow of a third channel, sushumna, is experienced.
Hatha yoga is a method of harmonizing the flow of pranas in the body and bringing the mind from a dissipated state to a focused state.