That implies you give it a lot of credibility, compared to "a grain of salt".
There are likely millions of salt crystals in a container. A "grain" weights 64.798 91 milligrams.
No, quite the opposite.
Take it with a grain of salt means check it; a million grains means check it a million times.
Taking something with a grain of salt refers to an ancient belief that salt neutralized many poisons.
To say you need more than a grain of salt implies that there is a lot of poison in something.