These volumes form part of the monumental project to produce the catalogue raisonné of Cassiano's ‘paper museum’ under the auspices of the Royal Collection and others. Cassiano dal Pozzo (1588–1657) came from a noble family well connected to the Medici family, and he spent his youth at the Medici court. He arrived in Rome in 1612, where he entered the service of Francesco Maria del Monte, and then of Cardinal Francesco Barberini, the nephew of Urban VIII. Both del Monte and Barberini were keen patrons of art, and collected antiquities as well as naturalia. Cassiano, like many cultural elites before and around him, had a passion for birds, catching and keeping them, and commissioning drawings and artwork of birds. The drawings were printed in Uccelliaria (1622), issued under the name of his master of household, Giovanni Pietro Olina, but reflecting Cassiano's own interests and views. This book marked Cassiano's admission in 1622 to the Accademia dei Lincei founded in 1603 by Federico Cesi (1585–1630). Cassiano's interest in the natural world expanded through his Lincean contacts, such as Johannes Faber; his correspondence with Nicolas-Claude Fabri de Peiresc; and his trips to Paris and Madrid. At the Escorial, he took notes on the manuscripts and drawings relating to Franciso Hernández's ‘Mexican treasures’, which the Linceans were trying to publish. It was Cassiano who had acquired Cesi's books, manuscripts and drawings after Cesi's death, and thus Cassiano's collection has come to include the pictorial archives of one of the most important scientific societies of the period, which included Galileo Galilei among its members.

As is the case with the entire corpus, these two volumes contain drawings of mixed origins: some were commissioned and collected by Cassiano or his younger brother Carl Antonio, others by Cesi, and there are several whose provenance is not entirely clear; not all of them were a result of first-hand observation and some objects depicted are no longer identifiable. The first volume, on the drawings of birds, begins with the general introduction to Cassiano's paper museum by the late Francis Haskell and Henrietta McBurney, and the introduction to the series of natural-historical drawings by David Freedberg. Paula Findlen's account of the development of Cassiano's interest in the study of nature is followed by McBurney's survey of the drawings of the birds. Like the format of these catalogues, each entry consists of text on left-hand page facing a colour reproduction of the drawing on the right-hand page, and, where necessary, additional illustrations are generously included, such as printed versions of the image or other images of the same object in related printed or manuscript works.

The second volume contains drawings of animals other than birds (quadrupeds, fish and crustaceans) commissioned and collected mainly by Cassiano, as well as drawings originally planned for the ninth volume of the natural-history series ‘minerals and natural curiosities’, reflecting some of Cesi's interests. Findlen's discussion of the scientific and cultural significance of the study of fauna in seventeenth-century Rome serves as an introduction to the drawings of animals other than birds. Caterina Napoleone and Ian Rolfe introduce the section on minerals and natural curiosities, which includes drawings of exotic nuts and seeds as well as scientific apparatus and ‘comet eggs’ from the second half of the seventeenth century. The extensive appendix helpfully includes extracts from the published account of Philip Skippon's visit to the collection in 1665, as well as Cassiano's correspondence and writings pertaining to birds. Several of these are transcribed from manuscript sources, and all are translated into English. Entries on birds were written by McBurney, Carlo Violani and Edward Dickinson; those on animals by Martin Clayton, Marco Masseti, Arthur MacGregor and Kathie Way; those on fish by Arturo Moralez Muñiz and Euforasia Rosello Izquierdo; those on minerals and stones by Ian Rolfe, Caterina Napoleone and Onno Wijnands; and Rea Alexandratos provided information on watermarks.

The drawings are mainly watercolour and bodycolour over black chalk on paper or on vellum. Blue paper is occasionally used for birds with white plumes (nos 66, 148) or objects woven of asbestos (nos 255–256). Most of the drawings of birds and minerals are attributed to Vincenzo Leonardi; the background landscapes of the bird drawings to Leonardi's teacher, Antonio Tempesta; a drawing of the cuckoo wrasse to Giovanna Garzoni (no 234); and a drawing of a coral to Cornelius Schwindt (no 298). Cassiano, an art connoisseur who knew Poussin, Bernini and other artists in Rome, found in Leonardi someone who could render visible his view of nature. As McBurney notes, Cassiano believed in the importance of form, texture and colour as distinguishing characteristics of birds and used the names of artists’ pigments to describe colour. Enlarged details of Leonardi's drawings helpfully illustrate how he built up form through layers of pigment which ‘perfectly’ matched Cassiano's interest (pp. 61–63).

Where possible, objects were drawn life-size, which occasionally meant the addition of a slip of paper to include the odd foot or fin which did not fit onto the original paper. With the exception of the drawing of birds in flight dated to the late sixteenth century (nos 179–180), most of the birds, fish and quadrupeds are represented in profile view. A view of the entire animal is often supplemented with details such as feathers (no 14), feet (nos 107, 137) or a paw (no 212).

Some studies, such as those of the flamingo (nos 121–122), the crane (no 129) and the pet marmot (nos 218–219), were done from living specimens, others from dead or stuffed samples (e.g. nos 116, 130). Some of the more exotic fauna came from the Roman menageries of the Borghese or the Barberini (e.g. the Somali ostrich, no 104, and the Dorcas gazelle, no 214). While transporting animals from far-flung places alive remained a challenge, samples of seeds and fruits were easier to transport and preserve. Drawings of these objects thus illustrate the global reach of European collectors at the time: a sand-box fruit (no 305) from tropical America, a fruit of the Jatobá locust tree (no 306) from the West Indies, a seed of the Raphia palm (no 308) from West Africa, a candlenut (no 309) from Indonesia and a Bambara groundnut (no 310) from Nigeria or Cameroon.

Publications served as a source of information as well as a guide to study. Carolus Clusius's work on exotic animals and plants remained an important source for naturalia which were difficult to get hold of, and the prints of European fish in Ippolito Salviani's book on aquatic animals (1554) were copied and coloured carefully (nos 224, 229, 230, 236). Georg Agricola's work on subterranean animals (1614) suggested which details of the crested porcupine to examine (no 217), and Ulisse Aldrovandi's owl's head in profile view in his ornithology (1599) was probably the source of a similar perspective of a barn owl (no 162).

The mineral section includes objects that Cesi considered to be of ‘middle nature’, such as corals, calcifying algae or fungus stone (nos 298–300). Furthermore the inclusion of stones created by animals (bezoars – nos 273–275) as well as humans (calculi, nos 272, 276) suggests an interest in the similarities between natural and human-made objects. Among a row of jasper objects is the first illustrated documentation of a carcara stone (no 259), a fusion of limestone with metallic oxides and copper powder to produce glass which looks like jasper. Life-size depictions of inlays of imitation marbles (nos 279–290) indicate further how artificialia and naturalia intersected in this collection. Apparently, Cassiano could tell apart the outputs of Roman and Florentine workshops of pietre dure (p. 597), which suggests the visual acuity of an art connoisseur. It would be interesting to know how it affected the way he saw nature's handiwork, or vice versa. For that, we would need to plough through not just the catalogues on natural history, but also those of antiquity, architecture and prints.

These volumes are a stark reminder of what is involved in understanding pre-modern ‘scientific’ drawings: a team of historians of art, historians of science and specialist curators working together over a period of time in order to flesh out the artistic, intellectual and social contexts in which these drawings came into existence and made sense as a way to capture and understand the natural world. The high standards of scholarship and precision, the colour reproductions, the concordances and appendix make these two volumes an invaluable basis for further research.