The person is told to set the hand of his watch at any hour he pleases,
which hour he tells you; and you add in your own mind 12 to it. You
then desire him to count privately the number of that addition on the
dial, commencing at the next hour to that at which he intends to rise,
and including the hour at which he has placed the hand; which will give
the answer; for example,
A intends to rise at 6 (this he conceals to himself;) he places the
hand at 8, which he tells B, who, in his own mind, adds 12 to 8, which
make 20. B then tells A to count 20 on the dial, beginning at the
next hour to that at which he proposes to rise; which will be 7, and
counting backwards, reckoning each hour as 1, and including in his
addition the number of the hour the hand is placed at, the addition
will end at 6, which is the hour proposed; thus,