I'd say any of the following
Composition 1960 #2’s instructions, for instance, are
Build a fire in front of the audience. Preferably, use wood although other combustibles may be used as necessary for starting the fire or controlling the kind of smoke. The fire may be of any size, but it should not be the kind which is associated with another object, such as a candle or a cigarette lighter. The lights may be turned out.
After the fire is burning, the builder(s) may sit by and watch it for the duration of the composition; however, he (they) should not sit between the fire and the audience in order that its members will be able to see and enjoy the fire.
The composition may be of any duration.
In the event that the performance is broadcast, the microphone may be brought up close to the fire.
5.5.60
Composition 1960 #3 has the following instructions:
Announce to the audience when the piece will begin and end, if there is a limit on duration. It may be of any duration.
Then announce that everyone may do whatever he wishes for the duration of the composition.
5.14.60
Composition 1960 #4:
Announce to the audience that the lights will be turned off for the duration of the composition (it may be any length) and tell them when the composition will begin and end.
Turn off all the lights for the announced duration.
When the lights are turned back on, the announcer may tell the audience that their activities have been the composition, although this is not at all necessary.
6.3.60
Composition 1960 #5:
Turn a butterfly (or any number of butterflies) loose in the performance area.
When the composition is over, be sure to allow the butterfly to fly away outside.
The composition may be any length but if an unlimited amount of time is available, the doors and windows may be opened before the butterfly is turned loose and the composition may be considered finished when the butterfly flies away.
6.8.60
Composition 1960 #7 denotes a B and F-sharp on a musical scale with the instruction that this fifth is “to be held for a long time.” Composition 1960 #15 is dedicated to Richard Huelsenbeck, one of the founders of Dada:
This piece is little whirlpools in the middle of the ocean.
Some people find it difficult to build a fire or catch a butterfly!