Full Idea
Does a Gedanke [thought] consist of words? No! But of psychical constituents that have the same sort of relation to reality as words.
Gist of Idea
A thought is mental constituents that relate to reality as words do
Source
Ludwig Wittgenstein (Letters to Russell [1919], p.125), quoted by Michael Morris - Guidebook to Wittgenstein's Tractatus 4B
Book Reference
Morris,Michael: 'Guidebook to Wittgenstein's Tractatus' [Routledge 2008], p.157
A Reaction
This is roughly my view of propositions, as non-lingustic mental events. The 'psychical constituents' seem to be concepts, in a psychological rather than a Fregean sense. This idea allowed transfer of his representation theory from thought to language.