Many mental processes admit of being roughly measured.  For instance,
the degree to which people are bored, by counting the number of their
fidgets. I not infrequently tried this method at the meetings of the
Royal Geographical Society, for even there dull memoirs are occasionally
read.  [...]  The use of a watch attracts attention, so I reckon time
by the number of my breathings, of which there are 15 in a minute.  They
are not counted mentally, but are punctuated by pressing with 15 fingers
successively.  The counting is reserved for the fidgets.  These observations
should be confined to persons of middle age.  Children are rarely still,
while elderly philosophers will sometimes remain rigid for minutes altogether.
		-- Francis Galton, 1909