How did Jiraiya find out Tsunade's breast size?


Jiraiya stated that Tsunade's _oppai_ size was **106cm**.

From [Tsunade article](http://naruto.wikia.com/wiki/Tsunade):

> Despite being known as flat-chested in her childhood, she now has a rather
> large bust; **106 centimetres** in circumference, according to Jiraiya.

From [Jiraiya article](http://naruto.wikia.com/wiki/Jiraiya):

> when caught spying on Tsunade in his younger years, she proceeded to break
> both of his arms, six of his ribs, and ruptured a number of organs as
> punishment.

Considering the amount of fear and respect Jiraiya then developed towards her,
**how did he know the measurement of the adult Tsunade?**

Source: <https://www.youtube.com/watch?v=ny7Fni193Jk>

(I'm really sorry about the quality of the video)

Below is the image from the corresponding scene in the manga (chapter 406,
page 9):

![](https://i.stack.imgur.com/qVJge.png)




Maybe Jiraiya transformed into Tsunade using a transformation technique and
found the size using traditional measures by measuring himself(!).

He may have used [Sexy
Technique](http://naruto.wikia.com/wiki/Sexy_Technique).

![](https://i.stack.imgur.com/39UEr.png)

