"The design of a temple depends on symmetry, the principles of which must be most carefully observed by the architect. They are due to proportion...Proportion is a correspondence among the measures of the members of an entire work, and of the whole to a certain part selected as standard. From this result the principles of symmetry. Without symmetry and proportion there can be no principles in the design of any temple; that is, if there is no precise relation between its members, as in the case of those of a well shaped man."

Vitruvius,

De Architectura (III.1.1)

The drawing (c.1492) is in the Gallerie dell' Accademia (Venice) but, given its fragile state, not on public display.