“Russian ladies, for the most part, cherish only Platonic love, without mingling any thought of matrimony with it; and Platonic love is exceedingly embarrassing.”
A Hero of Our Time (1840; rev. 1841)
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Mikhail Lermontov 34
Russian writer, poet and painter 1814–1841Related quotes
Source: The Friends of Voltaire (1906), Ch. 3 : Galiani : The Wit, p. 79

The Bill of Rights (1958), p. 73.
Extra-judicial writings

“[Matrimony] is the grave of love.”
Memoirs (trans. Machen 1894), book 5 (In London and Moscow), chap. 8 http://etext.library.adelaide.edu.au/c/casanova/c33m/chapter106.html (“She won’t believe it, as she knows my horror for the sacrament of matrimony.” “How is that?” “I hate it because it is the grave of love.”)
Referenced

This appears not to be a Kerouac quote. It has not been found in any of Kerouac's published work.
Misattributed