Question: What is generally referred to as the first Cubist picture?
About the article "Les Demoiselles d'Avignon", section "Cézanne and Cubism".

Candidate passages:
Both Paul Gauguin (1848–1903) and Paul Cézanne (1839–1906) were accorded major posthumous retrospective exhibitions at the Salon d'Automne in Paris between 1903 and 1907, and both were important influences on Picasso and instrumental to his creation of "Les Demoiselles."
According to the English art historian, collector and author of "The Cubist Epoch", Douglas Cooper, both of those artists were particularly influential to the formation of Cubism and especially important to the paintings of Picasso during 1906 and 1907. Cooper goes on to say however "Les Demoiselles" is often erroneously referred to as the first cubist painting.
He explains, 
The "Demoiselles" is generally referred to as the first Cubist picture.
This is an exaggeration, for although it was a major first step towards Cubism it is not yet Cubist.
The disruptive, expressionist element in it is even contrary to the spirit of Cubism, which looked at the world in a detached, realistic spirit.
Nevertheless, the "Demoiselles" is the logical picture to take as the starting point for Cubism, because it marks the birth of a new pictorial idiom, because in it Picasso violently overturned established conventions and because all that followed grew out of it.
Although not well known to the general public prior to 1906, Cézanne's reputation was highly regarded in avant-garde circles, as evidenced by Ambroise Vollard's interest in showing and collecting his work, and by Leo Stein's interest.
Picasso was familiar with much of Cézanne's work that he saw at Vollard's gallery and at the Stein's.
After Cézanne died in 1906, his paintings were exhibited in Paris in a large scale museum-like retrospective in September 1907.
The 1907 Cézanne retrospective at the Salon d'Automne greatly impacted the direction that the avant-garde in Paris took, lending credence to his position as one of the most influential artists of the 19th century and to the advent of Cubism.
The 1907 Cézanne exhibition was enormously influential in establishing Cézanne as an important painter whose ideas were particularly resonant especially to young artists in Paris.
Both Picasso and Braque found the inspiration for their proto-Cubist works in Paul Cézanne, who said to observe and learn to see and treat nature as if it were composed of basic shapes like "cubes, spheres, cylinders, and cones."
Cézanne's explorations of geometric simplification and optical phenomena inspired Picasso, Braque, Metzinger, Gleizes, Delaunay, Le Fauconnier, Gris and others to experiment with ever more complex multiple views of the same subject, and, eventually to the fracturing of form.
Cézanne thus sparked one of the most revolutionary areas of artistic enquiry of the 20th century, one which was to affect profoundly the development of modern art.
Picasso drew each of the figures in "Les Demoiselles" differently.
The woman pulling the curtain on the far right is rendered with heavy paint.
Composed of sharp geometric shapes, her head is the most strictly cubist of all five.
The heads of the crouching figure underwent at least two revisions from an Iberian figure to its current state.
Much of the critical debate that has taken place over the years centers on attempting to account for this multiplicity of styles within the work.
The dominant understanding for over five decades, espoused most notably by Alfred Barr, the first director of the Museum of Modern Art in New York City and organizer of major career retrospectives for the artist, has been that it can be interpreted as evidence of a transitional period in Picasso's art, an effort to connect his earlier work to Cubism, the style he would help invent and develop over the next five or six years.
Marie Bronislava Vorobieff-Stebelska (; 1892 – May 4, 1984), also known as Marevna, was a Russian-born Cubist painter.
She is internationally known for convincingly combining elements of cubism (called by her "Dimensionalism") with pointillism and – through the use of the Golden Ratio for laying out paintings – structure.
She tends to be accredited with having been the first female cubist painter.
Though having lived the greater part of her life abroad – her formative years as a cubist painter in France and her mature years in England –, she is often referred to as a "Russian painter".
From her relationship with the Mexican cubist painter and later muralist Diego Rivera in Paris she had a daughter, Marika Rivera (1919-2010), who herself went on to become a professional dancer and film actress. 
The painting's restraint and formal purity strongly appealed when Piero was first "discovered," especially to admirers of cubist and abstract art.
It has been held in especially high regard by art historians, with Frederick Hartt describing it as Piero's "most nearly perfect achievement and the ultimate realisation of the ideals of the second Renaissance period".
The painting is referred to in Len Deighton's 1978 novel, "SS-GB". 
Just as in painting, Cubist sculpture is rooted in Paul Cézanne's reduction of painted objects into component planes and geometric solids (cubes, spheres, cylinders, and cones).
And just as in painting, it became a pervasive influence and contributed fundamentally to Constructivism and Futurism.
Cubist sculpture developed in parallel to Cubist painting.
During the autumn of 1909 Picasso sculpted "Head of a Woman (Fernande)" with positive features depicted by negative space and vice versa.
According to Douglas Cooper: "The first true Cubist sculpture was Picasso's impressive "Woman's Head", modeled in 1909-10, a counterpart in three dimensions to many similar analytical and faceted heads in his paintings at the time."
These positive/negative reversals were ambitiously exploited by Alexander Archipenko in 1912–13, for example in "Woman Walking".
Joseph Csaky, after Archipenko, was the first sculptor in Paris to join the Cubists, with whom he exhibited from 1911 onwards.
They were followed by Raymond Duchamp-Villon and then in 1914 by Jacques Lipchitz, Henri Laurens and Ossip Zadkine.
Indeed, Cubist construction was as influential as any pictorial Cubist innovation.
It was the stimulus behind the proto-Constructivist work of both Naum Gabo and Vladimir Tatlin and thus the starting-point for the entire constructive tendency in 20th-century modernist sculpture. 
"Houses at l'Estaque" (French: "Maisons à l'Estaque") is a 1908 oil painting by Georges Braque.
It is considered either an important pre-cubist landscape or the first Cubist landscape.
The painting prompted art critic Louis Vauxcelles to mock it as being composed of cubes which led to the name of the movement.
It is a response to works by Paul Cézanne who also lived in L'Estaque at times.