Perseverance must have some practical end, or it does not avail the man possessing it. A person without a practical end in view becomes a crank or an… - Alexander Graham Bell

The inventor...looks upon the world and is not contented with things as they are. He wants to improve whatever he sees, he wants to benefit the world; he is haunted by an idea. The spirit of invention possesses him, seeking materialization.

Leave the beaten track occasionally and dive into the woods. Every time you do so you will find something you have never seen before. Follow it up, explore around it, and before you know it, you will have something to think about to occupy your mind. All really big discoveries are the result of thought.

There cannot be mental atrophy in any person who continues to observe, to remember what he observes, and to seek answers for his unceasing hows and whys about things.