The diagram to this beautiful geometric Tatou by Hiroko Yamada can be found in the monthly magazine NOA Nr. 114 from February 1985, called “Message case” and in the book “NOA Kessakusen 3“, p. 20-21.
This is another one of my favorite geometrical Origami Tatos. You start off by folding a square piece of paper into 4 x 4 sections. From there you need to fold and reopen parts and then fold down again – until you are left with this beautiful Origami Tato. You can finish this Japanese Origami Envelope into two different versions. The first version tucks the endings below and the second one more towards the top. Both look nice – and are easy to complete. I would recommend this Origami Tato Tutorial for intermediates and up. There is quite a bit of folding, opening and refolding – which could get confusing for a complete beginner.
The only material you will need is one square piece of paper. I used colored and white Origami paper. But you could also use only mono colored paper (copy paper). Medium size (15 cm x 15 cm / 6 in x 6 in) Origami paper results in a 7.5 cm x 7.5 cm / 3 in x 3 in Tato (measured outside) and a 5.3 cm x 5.3 cm / 2.1 in x 2.1 in inside square – for the letter or note.