How many of you ladies tried for a specific gender?

I know it’s just a theory but I’ve heard if you have sex a couple days before ovulation you are likely to have a girl, as they swim slower and live longer. If you want a boy you should have sex the day of ovulation or day after. Has anyone been successful with this? I know my cousin tried this and had a girl which is what she tried for but it could have just been coincidence.