Still, the curvature control device at Santa Maria del Fiore was
obviously a much larger instrument: if it was to stretch from the centre of
the dome to its circumference, the corda da murare must have been 70 feet
long at least. This unwieldy size would have presented certain problems.
F4ow, for example, was the cord prevented from sagging in the middle and
therefore causing inaccurate measurements? Was a system of pulleys used?
Or was it tautened and then smeared with wax like the ropes used by
surveyors in the Middle Ages?