Thinking tool

Source (and more photographs) here

This is a Nautilus shell, a ship of pearl with a lustrous coil and a heavenly message - according Oliver Wendell  in his poem "the chambered Nautilus".
In an audiobook I listened to today it was referred to as a "thinking tool" because of its logarithmic form, the Spira mirabilis,  the marvellous spiral. There, I have put the link in, so you can find out about all the mathematics.

The idea of a thinking tool appeals to me, and I look at my desk with new eyes. Yes, I could do with some thinking tools. At the office too. Not just thinking though, I want some inward-drawing tools as well. Don't know what they are yet. I will go in search of them.