The Theravadists stressed the painful, fleeting, and selfless character of all dharmas, all items of existence. Mahayanist philosophers riveted this interest onto emptiness with an almost ruthless intensity. Vajrayanist masters assumed it in their tantric meditations and rituals. Significantly, emptiness fades when we come to mainstream devotional Buddhism, as though it were too daunting for ordinary layfolk, whose need for colorful deities and rituals to incarnate general Buddhist doctrine into daily life pushed emptiness to the background. Indeed, by the time of the Burmese development of "karmic Buddhism" (concentration on merit), emptiness lay beyond the practical pale.
Inasmuch as Buddhist mysticism loves emptiness, it stands apart somewhat from Hindu mysticism. Anatman, selflessness, moves a step away from the Vedantic equation of atman and Brahman. How different the experiences of ultimate reality need be is hard to determine, but Buddhist mystics, especially those shaped by East Asian cultural influences, strike us as more fluid, spontaneous, in tune with the flow of nature than their Indian counterparts. This characterization is more descriptive than evaluative. It says nothing immediate about the comparative depth or richness of the two mystical complexes involved. However, it suggests some of the key implications of the romance of the Buddhist mystics with emptiness.
The last summary question that we raise is how Buddhist mysticism in general and emptiness in particular ought to incline us to think about our working description of mysticism as direct experience of ultimate reality. Minimally, it ought to incline us to think that the descriptions that mystics themselves work with can vary considerably. "Emptiness" is not a term prominent in the usage of Western mystics (though a little probing can turn up cognate, analogous terms: "nothingness," "contingency").
The Buddhist use of emptiness does not oppose it to light or mind. he figure is therefore flexible, as well as provisional (nirvana is ineffable, all figures are inadequate, more or less convenient). Similarly flexible is the movement of the human spirit of many Buddhist meditators. Still, whole, alert, poised, it is more like a feather than a rock, a bird than a hippopotamus. It is a dancer, a pilgrim, a wanderer that just may find the world fully congenial because it places no conditions on the world, strives to let the world be, move, just as the world chooses to do.