Verrocchio's Tombslab for Cosimo de' Medici
Designing with a Mathematical Vocabulary

The tombslab for Cosimo de' Medici is laid in the pavement in the crossing of the basilica of San Lorenzo in Florence. Its design is credited to Florentine sculptor Andrea del Verrocchio. It is very different from the kind of tomb markers of the early Renaissance: there is no bust or portrait of the deceased, and no explicit Christian symbols appear in the marker. To interpret the tombslab, it is necessary to study its geometrical forms and proportions. Far from being a terse pagan marker, it is a rich symbol for the cosmos and the Creator.

The geometrical forms in the composition refer to Humanist thought and neo-Platonic philosophy. In the center of the panel is a rectangle of red porphyry with sides which relate as 3:4. It is divisible into two 3:4:5 triangles, which have a long mathematical tradition. The addition of a half-circle to each side of the rectangle forms a "Solomon's Knot," symbolic of eternity. In the larger half-circles are almond shaped "mandorle," the fish-shaped symbol for Christ and the Eucharist. The composition is circumscribed by a circle, in its turn circumscribed by a square. As did the geometrical problem of squaring the circle, the circle in the square relates to the perfecting of the imperfect.

Proportions as well as geometric forms are exploited for expressive purposes. All the proportional relationships are based on the ratios of the five integers which make up the Ptolemaic musical scale. The use of these proportions implies a "harmonic" treatment of the elements of the composition, a phenomena which occurs quite frequently in Renaissance architecture.

The tombslab has been compared to three other pavements with which it is coeval: the Sistine Chapel, the Medici Chapel in the Palazzo Medici, and the Chapel of the Cardinal of Portugal in S. Miniato al Monte. Verrocchio's tombslab, however, is a forerunner of the ideas of greatest importance in pavement design of the fifteenth and sixteenth centuries, because of its emphasis on the concept of "center." By drawing the spectator into the center of the crossing, the tombslab introduces the element of living man into the composition. The design of Cosimo's marker makes reference to the order of the cosmos, and its placement in the center of the crossing is symbolic of man's central position in that cosmos.