The oldest mention of the staple right of Diez dates to the early 14th century and is an indication of significant shipping on the Lahn by that time. In 1559, John VI of Nassau-Dillenburg laid out a towpath on the lower Lahn. In 1606, for the first time, the Lahn was deepened to allow small scale shipping and the lower reaches became navigable for four to five months of the year. However, there were numerous weirs with only narrow gaps, so the traffic remained restricted to small boats.