Coffer. A coffer is a recessed panel. Ceilings covered with
coffers were known in ancient Greek architecture. They had
considerable importance in Roman houses (Vitruvius 7.2) and
temples and were occasionally used in Egyptian buildings in the
Roman, Byzantine, and early medieval periods. Coffers were made
in flat wooden ceilings by subdividing the space between the
large ceiling beams with short transverse beams. The areas thus
formed, usually rectangular, were closed off on top by boards,
which served as the substructure for the floor above. The beams
could either be adorned with carved work or covered with wood,
metal, or terra-cotta. In Roman vaulting, which usually
consisted of a concrete shell made of small chips of stone or
broken bricks and mortar, coffers were used as decorative forms
on the undersurface of the vault, since the recesses could be
very easily accommodated by the requisite thickness of the
vault. Such coffers could take on triangular or polygonal forms.
Famous examples are the vaults of