Halliday & Matthiessen (2004: 443):
Through projection, one clause is set up as the representation of the linguistic “content” of another — either the content of a ‘verbal’ clause of saying or the content of a ‘mental’ clause of sensing. … There are thus two kinds of projections. On the one hand, the projection may be a representation of the content of a ‘mental’ clause — what is thought; we call such projections ideas. On the other hand, the projection may be a representation of the content of ‘verbal’ clause — what is said; we call such projections locutions. Projection may thus involve either of the two levels of the content plane of language — projection of meaning (ideas) or projection of wording (locutions).