The time taken in making a round of the palm of the hand, neither very slow nor very quickly snapping the fingers once, is called Matra.
Each time-unit is called Matra. The twinkling of an eye is sometimes taken as the period of one Matra. Time occupied by one normal respiration is considered as one Matra. Time taken up in pronouncing the mono-syllable, OM, is regarded as one Matra. This is very convenient. Many Pranayama-practitioners adopt this time-unit in their practice.