"This map of New Spain is an enlarged version of Giacomo Gastaldi's published in 1548. The nomenclature is similar and cartographically it is identical with the noiceable exception of the Yucatan which is now shown correctly as a peninsula. There are clear signs, however, that the engraver first cut the plate to show an island, and his error was not completely erased when corrected. No example has been found in its insular form."

(Burden).

"Girolamo Ruscelli's re-engraved version of Gastaldi's important map - the first detailed map of Baja California, Mexico and the Gulf Coast. Gastaldi's original 1548 issue of this map is particularly scarce, so this is the earliest relatively obtainable map of the area [..]. Close examination of this plate indicate that, originally, when copied from Gastaldi's map, Yucatan was shown as an island. On this plate traces can be seen of an engraved coastline which has been obliterated and the peninsula has now been correctly delineated. This is an important map showing a more correct west coast cartography than was to be seen a hundred years later when California was shown on most maps to be an island.

(Potter).

"The first map to concentrate on the south-west area was the 1548 Gastaldi map, reissued in 1561 by Ruscelli".

(Potter).

"An enlarged re-engraving of the rare Gastaldi map of 1548, correcting the earlier map's depiction of the Yucatan as an island. This is the first separate printed map of the southern part of North America; the work's delineation of the region is vastly superior to other printed maps of the period, delineating the American Southwest, California, and the Gulf Coast in fine detail. California is a peninsula, and the Seven Cities of Cibola are recorded."

(Suárez).

Girolamo Ruscelli (1504 Viterbo -1566 Venice), an Italian Alchemist, Physician and cartographer, was editor of a revised and expanded Italian edition of Ptolemy's 'Geographia', published as 'La Geografia di Claudio Tolomeo. The newly engraved maps were based, generally, on those compiled by Giacomo Gastaldi for the Venice miniature atlas edition of 1548.

Ruscelli's atlas was issued several times between 1561 and 1599 by the following publishers

- Venice, Vincenzo Valgrisi, 1561
- Venice, Vincenzo Valgrisi, 1562
- Venice, G. Zileti, 1564
- Venice, G. Zileti, 1574
- Venice, Heirs of Melchior Sessa, 1598-99

The Ruscelli and Gastaldi atlases were the most comprehensive atlases produced between Martin Waldseemüller's 'Geographia' of 1513, and Abraham Ortelius 'Theatrum' of 1570. The significance of the Gastaldi and Ruscelli atlases cannot be overestimated. They defined the known geography of the world for decades. These atlases also reintroduced the use of copper engraving into the service of cartography, which was dominated by woodcut printing after several not very succesful attempts to print from copper in the 15th century. The Gastaldi and Ruscelli atlases proved that maps could be beautifully engraved on copper. As it was a harder material than wood, it was harder to engrave but also gave the ability to render much more detail. The Gastaldi and Ruscelli atlases marked a turning point in the history of cartography, from then on the majority of cartographic works used this medium.

"Ruscelli was editor of a revised and expanded edition of Ptolemy's Geographia which was issued in Venice several times between 1561 and the end of the century.

The newly angraved maps were based, generally, on those compiled by Giacomo Gastaldi for the Venice edition of 1548."

(Moreland & Bannister).