BOOKS ON ARCHITECTURE
Author(s) 
Cousin, Jean 
Title 
Livre de perspective 
Imprint 
Paris, J. Le Royer, 1560 
Localisation 
Paris, Ensba, Masson 403 
Subject 
Geometry, Perpective 
French
Jean Cousin
(1490?1560?), a painter from Sens who had settled in Paris around 1540,
made many drawings which were used as models for stained glass windows,
tapestries and engravings; he was also a geometer. His treatise on perspective
which appeared in 1560 has not come out in a new edition since then,
except in a facsimile (1974). In any case, it was mentioned in inventories
after the death of several artists and in works dating from the end
of the 16^{th} and the 17^{th} century, all of which proves a certain circulation
in the artistic milieu. In a foreward, “Jehan Cousin au lecteur”,
the author indicates a second volume devoted to the “figures de
touts corps, mesmes des personnages, arbres, & paysages, pour entendre
& cognoistre en quelle situation, forme & grandeur ilz doivent
estre representez selon cest art” [of perspective], but he died
before it could be published. Jean Cousin, the son, the author of a
treatise on this subject, the Livre de Portraiture (1595, and
regularly republished up until the 19^{th} century), in which the individuals
are drawn in perspective, probably reused a part of the material left
by his father.
The Livre de perspective is rarely studied, and one often thinks
that it apparently took up again, without adding anything new, the great
principles of the traditional construction of an image in perspective:
the lines perpendicular to the “ligne Terre” (the horizontal
base of the plane) converge towards a point (the vanishing point) placed
on the horizon; whereas the space between the lines parallel to the
“ligne Terre” steadily decreases. In the De artificiali
perspectiva (Toul, 1505) Jean Pèlerin, also known as Viator,
perfected a method based on two “tierspoints” equidistant
from the vanishing point, on the horizon line, to calculate the decreasing
depths of the parallel lines. This method was adopted and perfected
by Jean Cousin, who gave new geometric rigour to his account.
The Livre de perspective, made up of 58 chapters (141 unnumbered
pages), follows a plan in three parts: the putting in perspective of
plane figures, then figures in three dimensions, finally come examples
of edifices, stairways, columns, and geometric volumes (among which
are the “cinq corps réguliers” mentioned in Plato's
Timaeus, in Euclid or in Dürer's Underweysung der messung, 1525). Cousin's plan is simple and rigorous: he states
problems of increasing difficulty and considers several cases each time.
The clarity of his demonstrations stems from the book's large format,
and from the elegance of the sketches (drawn by the author himself on
wooden plates to be engraved), in which letters allow one to refer easily
and quickly to the explanatory text .
The most important one of Cousin's innovations in relation to Viator's
method consisted in distinguishing between two different sorts of planes
to draw a figure in perspective. One of these two planes is drawn above
the other: the géométral plane, that is to say
orthogonal, in which the figures undergo no optical deformation; and
the perspective plane, determined by the vanishing point and the two
“tierspoints”. One obtains a drawing in perspective by
transferring the coordinates of the figure determined in the orthogonal
plane. .
In Viator's tradition, Cousin gave preference to the question of the
“tierspoints”, that is to say calculating the reduction
of spaces in depth. The first rule of the treatise “demonstre
la source & origine de cest Art de Perspective […], car par
icelle vous sera monstré comment il faut extraire toutes profonditez
& longitudes”. And the last rule focuses on two demonstrations
exclusively concerning the “profonditez”, one backed up
by an optical experiment, the other by a geometrical figure in which
circles and squares alternate. It was traditionally used in mathematical
works. The importance given to “tierspoints” could seem
surprising today when studies often concentrate on the vanishing point.
But for a novice draftsman, to whom the Livre de perspective
was aimed, setting the vanishing point did not mean any great difficulty,
any more than making perpendicular lines converge towards it. On the
other hand, the “tierspoints” which define the reduction
of parallels in depth are handled more delicately, and their effect
on the point of view adopted by the representation is more complicated
to explain. Thus Jean Cousin does not suggest a theory of perspective,
but he wants to adapt to the painters' needs and he claims to regulate
their practice.
Through his rigorous approach, Jean Cousin contributed in imposing the
idea that the construction of an image in perspective responds to a
corpus of geometrical rules which must all be systematically imposed.
Thus he participated in a scientific reevaluation of perspective.
Valérie Auclair (Université ParisEst, MarnelaVallée)
– 2005
Critical bibliography
V. Auclair, Dessiner à la Renaissance. La copie et la perspective comme instruments de l'invention,
Rennes, Presses Universitaires de Rennes, 2010.
V. Auclair, "La Quadrature dans le livre de Perspective de Jean Cousin (1560). Réflexions sur l'histoire d'une notion", M. Bleyl & P. DubourgGlatigny (ed.), Quadratura: Geschichte, Theorie, Techniken, Berlin/Munich, Deutscher Kunstverlag, 2011, pp. 6580.
C. Grodecki, Documents du Minutier central des notaires de Paris.
Histoire de l'art au XVI^{e} siècle, Paris, Archives nationales,
19851986. 2 vol.
G.M. Leproux, La Peinture à Paris sous le règne
de François I^{er}, Paris, PU ParisSorbonne, 2001.
H. Zerner, L'art de la Renaissance en France. L'invention du classicisme,
Paris, Flammarion, 1996.
