Watercolour and ink. 6¾ x 6¼in. (17.3 x 16.3cm.)Monogrammed lower left and dated ’78. ProvenanceNT.The dictionary defines a tessaract as a four dimensional cube or hypercube. The fourth dimension is often regarded as the spiritual dimension. For Colquhoun, the hypercube was of magical rather than mathematical interest. She introduces spatial and depth ambiguities into the form of the cube by the use of different coloured facets and transparent washes. In other words, she has endeavoured, on a two dimensional sheet of paper, to depict a three dimensional representation of the shadow of a four dimensional object.Preparatory sketches, colour notes and a written description of her method all survive.