The ancient science of bioenergy given through the Vedas states that there are numberless billions of solar systems of which our planet is a tiny speck. The layer of useful atmosphere surrounding our planet Earth is very thin. Any change induced in this layer of atmosphere auto-matically leads to a corresponding change in PRANA, the life energy that pulsates through us all and connects man with the cosmos. Prana and mind may be taken to be like two sides of the same coin and hence, a change in the atmosphere is automatically transposed to the realm of the mind.
The Vedic science of Yajnya states that mind is affected by rhythms of nature corresponding to undulations of our planet. Yajnya is a process based on biorhythms of which man is a prisoner. Various rhythms of nature corresponding to the rotation of the Earth and other cosmic objects affect the human body and mind. Burning specific organic substances into fire and uttering certain Mantras under the conditions of certain rhythms of nature produce a specific effect in the atmosphere. This is modus operandi of YAJNYA. The resultant effect is carried to the realm of the mind and mind becomes tranquil. Our happiness depends on the reactions of the mind and hence, Yajnya is a material aid to happy life AGNIHOTRA is the smallest form of Yajnya based on one circadian rhythm corresponding to sunrise and sunset. Thus, burning of specific substances and uttering of Mantra are to be sychronized with the timing of sunrise and sunset. This, in short is Agnihotra, the smallest Yajnya which anyone in any walk of life can practise with a little effort.
The fire is to be prepared in a copper vessel which has a pyramid shape. The metal itself, as well as the shape, have an effect on the subtle energies which induce a change in the atmosphere leading to a beneficial change on the mind. Agni-hotra is a great material air to unburden the mind and you begin to feel free. Practice of Agni-hotra automatically insures that the change in rhythm will be in tune with nature. This avoids a disharmony in equilibrium and thus proneness to disease is lessened.
The entire process of a Yagna, consisting of mantra chanting, lighting the sacrificial fire and offering havis (food) to the gods in the form of ghee, Vanaspati (materials from plants and trees) and other objects, purifies the environment significantly. The Vedas prescribe a variety of Vedic rituals having different standards and goals.
These rituals are classified as - Sroutha Karmas & Smartha Karmas. Rituals like Marriage, Upanayana, Grihapravesam, Ganapathi Homam and such others are Smartha Karmas. Agnihotra, Ishti, Somayaga etc are Sroutha Karmas.
These Sroutha Karmas are of 21 types classified as Pakayagnas, Haviryagnas & Somayagnas each consisting of seven varieties of yagnas. Out of these 21 nityakarmas, only the Agnihotra and the Aupasana are to be performed twice daily, at dawn and dusk. The remaining ones have certain allotted frequencies over the course of the year. The more complicated the yagya, the less frequently it is performed. The most complex ones need to be performed only once in a lifetime. The yagna that involves the extraction, utility and consumption of Soma (in the general sense nectar, but extract of a particular tree) is called a Soma Yagna. Others are usually referred to as haviryagnas.
Paakayagnas are stated in Grihya sutras. So they are known as Grihya karmas. The seven Paakayagnas are ataka, sthālipāka, parvana, srāvaṇi, āgrahayani, caitri and āsvīyuji
The seven Haviryagnas are agniyādhāna, agnihotra, darśa-pūrṇamāsa, āgrayana, cāturmāsya, niruddha paśu bandha, sautrāmaṇi
The seven Somayagnas are agnistoma (for the atmosphere), atyagnistoma (for water), uktya (for food), shodasi (for health), vājapeya (for peace of mind), atirātra (longevity of life) and aptoryama (for well-being, prosperity of the whole society)