Muratori gives a treaty, written in Latin, of the year 1193, between the citizens of Bologna and Ferrara, which contains a list of those articles subject to pay duty. Among these occurs _indigum_[641]. In the thirteenth century, the celebrated Marco Polo, who spent twenty-six years in travelling through Asia, and even some parts of China, relates that he saw indigo, which the dyers used, made in the kingdom of Coulan or Coilum; and he describes the process for preparing it[642]. Much curious information in regard to the trade with this article, in the middle of the fourteenth century, is contained in the valuable work of Francesco Balducei Pegolotti[643]. We there find the names of different kinds, such as _Indaco di Baldacca detto buccaddeo_, in all probability from Bagdad, a city which in many old books of travels is called Baldach or Baldac; also _Indaco del Golfo_, _Indaco di Cipri_, _Indaco Rifanti_. Indigo, at that time, was imported in hides (_cuojo_), or in leather bags (_otre_), and also in boxes (_casse_). What this traveller says in regard to the signs by which its goodness may be known, is very remarkable. Nicolo Conti, who travelled through India before the year 1444, mentions _endego_ among the merchandise of Camboia[644]. That the expression _color indicus_ was used in the middle ages to denote blue mixed with violet, is proved by Du Cange. It appears to me therefore highly improbable that indigo should not be known to Rosetti, as Professor Bischof supposes[645]. In that important work on dyeing, however, which I mentioned long ago[646], it occurs several times, and always under the name _endego_.