Stephen Johnson Field,
Pico v. United States (69 U.S. 279…
“ When, therefore, a claim to land in California is asserted under an alleged grant from the Mexican Government, reference must, in the first instance, be had to the archives of the country embracing the period when the grant purports to have been made. If they furnish no information on the subject, a strong presumption naturally arises against the validity of the instrument produced, which can only be overcome, if at all, by the clearest proof of its genuineness, accompanied by open and continued possession of the premises. ”
