Meikyo-shisui is a very good expression to know how our mind should be. Let me explain what kanjis mean.
Meikyo means "a clear mirror". It is a clean mirror so you see no dust, clouds or condensation on it.
The kanji itself says, "shining mirror". So you can imagine how clean the mirror is.
Shisui means "the water that is not moving", the still water. If the water is still, completely still, it can reflect anything like a mirror.
So what do you think it means? So what kind of state of mind is it when it is like the really clean mirror and the still water?
When a mirror is dirty or it has something on it, it does not reflect things as it should. So it is not working as it is supposed to do. When your mind is not clear, your mind does not work as it is supposed to, either.
Moreover, when your mind is not clear or clean, it is usually mean that something evil thing is going on in your mind.
So there are two meanings in keeping your mind as clear as a clean shining mirror. One is that your mind and head is so sharp and clear that you will not misjudge anything. Another meaning is that you do not have any evil thoughts in you.
Here is an example using another kendo term. When your mind is clear, your mind is not in the state of "shikai".
And if you have evil thoughts, you are not following the kendo teachings.
Shisui is the still water. Your mind should be like the still water. So if your mind is still like the still water, how do you think you would feel? Peaceful, right?
Are you familiar with the concept? Peaceful mind? Yes. It is heijoshin.
When our mind was wavy like the sea on a stormy day, it would affect our judgement and behaviour. So if we could keep our mind as still as the still water, we can keep our mind in the state of heijoshin.
And there is one more. Meikyo and shisui both can reflect things very well. So it also means that if the state of your mind is like meikyo andshisui, you can reflect the mind of your opponent. It means you could tell what your opponent would do.
Wow! Isn't it great? How is that possible? Well, I don't know. But I can give you an example.
If you train with high ranked people like 7th dan or 8th dan, they won't let you do what you want to do as if they knew what you were thinking.
They will strike you however you move as if they knew how you would react to their moves.
I am not sure if they can reflect our thoughts in their mind but they act like they do. That is the fact. Let's train hard and try to get there!