Mengel was born on 23 October 1716 in Schweidnitz, Silesia, the son of tailor Christian Friedrich M. and his wife, née Reinert.
Preuss had just acquired the exclusive rights to the publication of Ludvig Holberg's Niels Klim and published it in both Latin, German, French and Danish.
He purchased the rights to Holberg's books from Preuss' creditors and published extended versions of Niels Klim in Latin (1745), German and Danish.
He got hold of a copy of Don Ranudo, which Holberg had completed back in 1723 but not dared to publish for fear that it would be perceived as a satire on the Danish nobility.
Holberg took revenge by granting Ernst Heinrich Berling, his publisher since 1742, the exclusive rights to a new, revised translation into Danish.