He who can say how he burns is in but a little fire.

To be able to say how much you love is to love but little. | "[To Laura in Death, canzone] 137", as reported in Bartlett's Familiar Quotations (1968), p. 163. (Bartlett’s references an older edition of the Canzoniere where sonnets (and other verse types) are numbered separately. This is from sonnet 137 which translates to canzone 170 when numbered through. The translation of chi pò dir com'egli arde, è 'n picciol foco is quite liberal.)