In the Spain of 1909, the Valencian sculptor and painter Ricardo Causarás registered a patent of a flying machine with a, now, well-known shape. His “Aeroplano” was a sharp angled delta monoplane, according to his advocates, the first registered use of that wing platform.
Causarás started its aeronautical experiments in 1905, building under military sponsorship -and secrecy- a small prototype. Later, in 1909, two further prototypes were produced (one small and the other quite bigger) at the very Valencian Barrio del Carmen. Those two were tested nearly, yet few data is available about those tests. Anyway, by then the confidential nature of the Causarás’ work seems to have ended: his flying endeavours were profusely published in the diaries.
By the way, I use to stroll near the place where Causarás built his last two “aeroplanos”.