This is most certainly the most charming mix of East and West I have ever seen in tea ceremony. It allows the host to wear proper western dress without compromising the Japanese elegance of the temae. I wish it had more popularity than the usual methods of tucking in the fukusa when in Western dress, which just look awkward and inconvenient.

WesternFukusa1The Basics of Mushanokoji-senke style Tea by SEN Soujuu

The Fukusa when in Western Clothing
In modern life, both men and women are increasing experiences occasions to make tea while wearing Western clothing. Here we talk about how to use the fukusa in such situations.
Because we do not put soiled items into the breast pocket of a dress jacket, it is a clean place. When wearing Western clothing, let’s tuck the fukusa in there.
(32) Just as we normally do, take the fukusa at point A with the right hand and point C with the left hand and fold it into a triangle.
(33) Then bringing corners of A and C together, hold them together with the right thumb.
(34) Hold it laying corners B and D together and bring it in front of your body.
WesternFukusa2(35) Fold up one third on the right side.
(36) Then fold over that one third on the left side and hold the shape in the right hand.
(37) Put it into your breast pocket just like that!
(38) When performing fukusa-sabaki during the temae, first take it out of your pocket with your right hand.
(39) Without disarraying the shape, switch it to your left hand.
(40) Then, take corner A, which will be the layer at the very bottom, with your right hand.
(41) Let the fukusa fall open over your left knee. After that, continue with fukusa-sabaki as normal.

茶の湯全書by主婦の友社編
主婦の友社、東京(1956)

武者小路千家の点前基礎:洋服のときのふくさ(p398-9)by千・宗守
現代の生活では、男女ともに洋服で茶をたてる機会がふえてきました。そのときのふくさ扱いについてのべましょう。
洋服の胸のポケットには、よごれたものをいれませんから、清らかです。洋服のときはこゝを利用して、ふくさをつけます。
(32)いつものように、右手でA、左手でC、と三角に折って持ったふくさを、両手を寄せて手前に二つに折り、
(33)AとCを重ねて右指に持ち、
(34)左指でBとDの重なりを持って、体正面にかまえます。
(35)右側三分の一を折り、
(36)その上に左側三分の一を折り重ねて、右手に渡し、
(37)そのまゝ胸のポケットに入れます。
(38)お手前の中で、ふくささばきをするときは、まず右手でポケットから抜き出し、
(39)そのまゝの向きで左手に持たせ、
(40)このとき、いちばん下側に見えるAを右手でとって、
(41)左膝頭にたらし、あとは、普通のふくささばきと同様に(8)(9)(10)・・・とつゞきます。