As many as three glissandi can be played simultaneously in each hand.
Three fingers slide simultaneously over the strings forming a cluster or a triad. The interval between the fingers should be approximately a third.
Double glissando upwards, triple glissando downwards.
The normal glissando notation is doubled or tripled.
A single or double glissando in one hand is louder than a triple one. This is because in order to fit three sliding fingers on the strings together, the hand has to be at an awkward angle and therefore loses power. Furthermore, when the sliding fingers are close to each other, one finger damps the resonance of the strings played by its predecessor.