by Paul-Yves Pezron on Breton. Grammars of European languages other than Latin and Classical Greek began to be published at the end of the 15th century. This led to comparison between the various languages. In the 16th century, visitors to India became aware of similarities between Indian and European languages. For example, Filippo Sassetti reported striking resemblances between Sanskrit and Italian. Early Indo-European studies In his 1647 essay, Marcus Zuerius van Boxhorn proposed the existence of a primitive common language he called "Scythian". He included in its descendants Dutch, German, Latin, Greek, and Persian, and his posthumously published Originum Gallicarum liber of 1654 added Slavic, Celtic and Baltic. The 1647 essay discusses, as a first, the methodological issues in assigning languages to genetic groups. For example, he observed that loanwords should be eliminated in comparative studies, and also correctly put great emphasis on common morphological systems and irregularity as indicators of relationship. A few years earlier, the Silesian physician Johann Elichmann (1601/1602–1639) already used the expression ex eadem origine (from a common source) in a study published posthumously in 1640. He related European languages to Indo-Iranian languages (which include Sanskrit). The idea that the first language was Hebrew continued to be advanced for some time: Pierre Besnier (1648–1705) in 1674 published a book which was translated into English the following year: A philosophical essay for the reunion of the languages, or, the art of knowing all by the mastery of one. Leibniz in 1710 proposed the concept of the so-called Japhetic language group, consisting of languages now known as Indo-European, which he contrasted with the so-called Aramaic languages (now generally known as Semitic). The concept of actually reconstructing an Indo-European proto-language was suggested by William Wotton in 1713, while showing, among others, that Icelandic ("Teutonic"), the Romance languages and Greek were related. In 1741 Gottfried Hensel (1687–1767) published a language map of the world in his Synopsis Universae Philologiae. He still believed that all languages were derived from Hebrew. Mikhail Lomonosov compared numbers and other linguistic features in different languages of the world including Slavic, Baltic ("Kurlandic"), Iranian ("Medic"), Finnish, Chinese, Khoekhoe ("Hottentot") and others. He emphatically expressed the antiquity of the linguistic stages accessible to comparative method in the drafts for his Russian Grammar published in 1755: Imagine the depth of time when these languages separated! ... Polish and Russian separated so long ago! Now think how long ago