This question is about crypto currency but can be as general as capital gains tax

Let's say I invested 20, 000 total in 4 years.

My investments have grown.

I want to take out my initial investment, and leave the rest in the stock/crypto.

I shouldn't be taxed on my initial investment because that's was already after tax money. Right?

I am aware of " cost based "

Ex;

Bought 1 share at 100$, the share doubled so now I have 1 shares at 200$. I want to take out my initial investment of 100 $ leave the profit of 100 in.

Based on cost base I sell .5 of the share to get 100$ back I would be taxed on the rise of the share from when I bout to the value of when I sold.

After 4 years I just put money in without thinking of selling. So I don't have all my cost base.

Is it all possible just to prove the amount I put in and take the same amount of money out without being taxed?

And later on just pay capital gains on the rest since I withdrew the initial investment?

Hope my question isn't too complicated to understand..

In short. Would like to know if possible to prove money I put in without proving what I bought and sold and take at that amount tax free