Blue Switch (Super Mario 64)
From the Super Mario Wiki
When Mario finds a Blue Switch and Ground Pounds it, Blue Coins show up nearby. Mario has a short time to gather the Blue Coins, after which they disappear. The block cannot be reused. The amount of Blue Coins that appear varies with each course, ranging from two to ten or more; they are often necessary to obtain the 100-coin Power Star from the levels they appear in. During the time that Blue Coins appears on the screen, a timer can be heard, which ticks faster when the time is running out.