During the Middle Ages, major cities had their own set of measures and the public availability of these standards allowed visiting merchants to comply with local regulations. The official Viennese ell length standards for verifying the measure of different types of cloth sold are embedded in the cathedral wall, to the left of the main entrance. The linen ell, also called Viennese yard, () and the drapery ell () length standards consist of two iron bars. According to Franz Twaroch, the ratio between the linen ell and the drapery ell is exactly formula_1. The Viennese ells are mentioned for the first time in 1685 by the Canon Testarello della Massa in his book "Beschreibung der ansehnlichen und berühmten St. Stephans-Domkirchen".