describing the system of weights
and measures in use in the Great Place
Linear Measure
Linear measure is based on three units: the thumb, the span,
and the manheight. A manheight is just less than two metres; a
span is one eighth of this, and a thumb is one eighth of a span
(just more than an inch, or approximately the length of the top
joint of a thumb). Larger measures are given in thousand
manheights (remembering that one thousand octal is 512 decimal,
one thousand manheights is a bit more than a kilometre).