The crowd, suddenly there where there was nothing before, is a mysterious and
universal phenomenon. A few people may have been standing together -- five, ten
or twelve, nor more; nothing has been announced, nothing is expected. Suddenly
everywhere is black with people and more come streaming from all sides as though
streets had only one direction. Most of them do not know what has happened and, 
if questioned, have no answer; but they hurry to be there where most other
people are. There is a determination in their movement which is quite different
from the expression of ordinary curiosity. It seems as through the movement of 
some of them transmits itself to all the others. But that is not all; they have
a goal which is there before they can find words for it. -p 16

Crowd crystals are the small, rigid groups of men, strictly delimited and of
great constancy, which serve to precipitate crowds. Their structure is such 
that they can be comprehended and taken in at a glance. Their unity is more
important than their size. -p 73

From Elias Canetti's "Crowds and Power" (1962).