timaeus   

again divided this whole into as many portions as was fitting, each
portion being a compound of the same, the other, and the essence.
And he proceeded to divide after this manner:-First of all, he took
away one part of the whole [1], and then he separated a second part
which was double the first [2], and then he took away a third part
which was half as much again as the second and three times as much
as the first [3], and then he took a fourth part which was twice as
much as the second [4], and a fifth part which was three times the
third [9], and a sixth part which was eight times the first [8], and a
seventh part which was twenty-seven times the first [27]. After this
he filled up the double intervals [i.e. between 1, 2, 4, 8] and the
triple [i.e. between 1, 3, 9, 27] cutting off yet other portions
from the mixture and placing them in the intervals, so that in each
interval there were two kinds of means, the one exceeding and exceeded
by equal parts of its extremes [as for example 1, 4/3, 2, in which the
mean 4/3 is one-third of 1 more than 1, and one-third of 2 less than
2], the other being that kind of mean which exceeds and is exceeded by
an equal number. Where there were intervals of 3/2 and of 4/3 and of
9/8, made by the connecting terms in the former intervals, he filled
up all the intervals of 4/3 with the interval of 9/8, leaving a
fraction over; and the interval which this fraction expressed was in
the ratio of 256 to 243. And thus the whole mixture out of which he
cut these portions was all exhausted by him. This entire compound he
divided lengthways into two parts, which he joined to one another at
the centre like the letter X, and bent them into a circular form,
connecting them with themselves and each other at the point opposite
to their original meeting-point; and, comprehending them in a
uniform revolution upon the same axis, he made the one the outer and
the other the inner circle. Now the motion of the outer circle he
called the motion of the same, and the motion of the inner circle
the motion of the other or diverse. The motion of the same he
carried round by the side to the right, and the motion of the
diverse diagonally to the left. And he gave dominion to the motion
of the same and like, for that he left single and undivided; but the
inner motion he divided in six places and made seven unequal circles
having their intervals in ratios of two-and three, three of each,
and bade the orbits proceed in a direction opposite to one another;
and three [Sun, Mercury, Venus] he made to move with equal
swiftness, and the remaining four [Moon, Saturn, Mars, Jupiter] to
move with unequal swiftness to the three and to one another, but in
due proportion.
Now when the Creator had framed the soul according to his will, he
formed within her the corporeal universe, and brought the two
together, and united them centre to centre. The soul, interfused
everywhere from the centre to the circumference of heaven, of which
also she is the external envelopment, herself turning in herself,
began a divine beginning of never ceasing and rational life enduring
throughout all time. The body of heaven is visible, but the soul is
invisible, and partakes of reason and harmony, and being made by the
best of intellectual and everlasting natures, is the best of things
created. And because she is composed of the same and of the other
and of the essence, these three, and is divided and united in due
proportion, and in her revolutions returns upon herself, the soul,
when touching anything which has essence, whether dispersed in parts
or undivided, is stirred through all her powers, to declare the
sameness or difference of that thing and some other; and to what
individuals are related, and by what affected, and in what way and how
and when, both in the world of generation and in the world of
immutable being. And when reason, which works with equal truth,
whether she be in the circle of the diverse or of the same-in
voiceless silence holding her onward course in the sphere of the
self-moved-when reason, I say, is hovering around the sensible world
and when the circle of the diverse also moving truly imparts the
intimations of sense to the whole soul, then arise opinions and