Looking at Donder who was so excited, Zhang Tie became stunned as he had not imagined that such righteous words could come from that mean guy. What made him even more amazed was that the book <Mental Arithmetic by Abacus> that he had picked up from the roadside stall could play such a huge role.
Everything that had happened today made Zhang Tie muddle-headed. Soon after, he recovered his composure, realizing a lot of useful information from Donder's words.
First, the cultivation of spiritual energy mainly relied on visualizations. However, before the secret of 'Mental Arithmetic by Abacus' was discovered, it seemed that the greater part of methods being used to cultivate one's spiritual energy were very sophisticated and hard to master. It was an especially tough challenge for young people and kids not yet twelve years old as they didn't have a stable temperament.