Represent the natural number with P.
Choose another number smaller than P and represent this number with Z. For example, if P = 6, then choose Z = 3 or Z = 2.
Find the average of Z and P/Z, and represent this result with A. The average A = [Z + (P/Z)]/2. For example, if P = 6, and Z = 3, then the average A = [Z + (P/Z)]/2 = [3 + (6/3)]/2 = 5/2 = 2.5.
Use the value of A calculated in step 3 as a replacement for the value of Z. For example, if P = 6 and Z = 3 so that A = 2.5, then the new value for Z = 2.5.
Repeat steps 3 and 4 until Z and (P/Z) are approximately the same value. For example, if Z = 2.5, it follows that (P/Z) = (6/2.5) = 2.4. The difference between 2.5 and 2.4 is 0.1. Steps 3 and 4 are repeated until this difference is equal to or close to zero.
Set the square root of the natural number P to be Z when Z = P/Z. For example, when P = 6, the final value for Z = 2.45 = P/Z = (6/2.45).