In Hinduism, Yajna (also Yaga or Yagya) is a type of sacrifice performed to please the Devas. It involves pouring oblations into the divine Agni (the sacrificial fire). Everything that is offered in the divine Agni is believed to reach the Devas. A yajna is typically performed by a pundit, with a number of additional pundits playing a supporting role, chanting Sanskrit verses. Often there will be a fire in the centre of the stage and items are offered into the fire. The range and expense of the items thrown on the fire can be surprising - including many whole coconuts, large quantities of ghee, sandalwood shavings and even quantities of clothing. A yajna can go on for several hours, typically with the whole village turning up to witness.
While yajnas clearly have a religious origin they also appear to have a subtle effect on the level of consciousness.