Full Idea
Descartes denies any similarity between the physical world and ideas, as matter possesses only geometrical properties; Locke allows more primary qualities, but follows Boyle and the atomists in treating secondary qualities as creations of sense.
Gist of Idea
For Descartes, objects have one primary quality, which is geometrical
Source
report of René Descartes (Meditations [1641]) by Howard Robinson - Perception 1.5
Book Reference
Robinson,Howard: 'Perception' [Routledge 2001], p.15
A Reaction
The interesting point to note here is that Descartes' geometrical view of objects (they are defined purely by 'extension') is the view that they have one minimal primary quality. I prefer Locke's view, of which the history (given here) is interesting.