At first sight, without practice, by sight-reading.
Mid 19th century; earliest use found in Edward Holmes (?1797–1859), music critic. Apparently from Italian prima vista (in adverbial phrases, e.g. in prima vista, alla prima vista, nella prima vista, a prima vista, all in sense ‘at first sight’) from prima, feminine of primo first + vista sight, view. Compare German prima vista (1874 or earlier in musical use, both in titles of musical works and in compounds such as Prima-Vista-Klavierschule, Primavista-Spiel).